When to drone and when not to drone can be very confusing. The problem with playing Zerg at lower levels is that Zerg is the only race that has to constantly choose between mining units and offensive units. When a terran moves out with 10 marines, if he’s been constantly producing SCVs, there’s no problem. If a Zerg moves out with 20 zergling, however, those 20 zergling represent a lost 10 drones, so he MUST do something worthwhile with them, otherwise they are wasted resources.

A good rule of thumb is to try to drone up to 2 drones per mineral patch. That means 16 drones mining resources. If you double click a drone in a mineral field, there should be 2 full rows of drones. 2 full rows + 4 more drones if you’re mining both gas (4 drones instead of 6, since 2 are hidden inside of the extractors). You should avoid making offensive units at all costs until you ABSOLUTELY need them, otherwise you miss out on having more drones, earlier, which could be mining earlier, which would help you build a larger army later!

Good Luck, Have Fun.

In the former, both players are generally sitting in defensive positions while one player pulls a small part of his force away (generally in a dropship/overlord) and sends it to what he believes to be an undefended part of his opponent’s base. Typically the player will be aiming to deal either economic (killing workers), technological (destroying key tech buildings), or production (destroying unit producing buildings) damage.

In the latter, one player generally has his army poised to attack, but then sends a small group of units away to harass the opponent’s base, hoping the opponent pulls more than what’s necessary to kill it. While the opponent is distracted dealing with the harass, the player will then attack, hoping to catch the opponent both off guard and out of position.

There are dozens of ways to go about harassing effectively, so I’ll leave that for another post. For this post here, I merely want to get one point across – it’s very hard to tell when your opponent is trying to do damage with a harass and when he’s simply trying to pull you out of position. In fact, he can do both things at once, sometimes. It is very important, when being harassed, to send the minimal number of units possible to deal with it. If someone drops 8 marines in your main, pull 10-12 lings and maybe your muta flock (or a couple banelings, or 2 infestors, depending on what build you’re doing) to deal with it. Leave your main army in position so you’re ready if your opponent attacks and don’t over-commit to defending small harasses.

Don’t ever over-defend harasses, or you’ll find yourself getting harassed into defeat quite often against higher caliber opponents. Good Luck, Have Fun

Overlords are like a free maphack for zerg players. You should do your best every single game to try to spread overlords to as many “safe” spots as possible. “Safe” spots are best described as areas on the map where you don’t think the overlords will be picked off without gaining something valuable in return. For example, spreading overlords over open air space around your main base is a great way to detect drops. Putting 1 overlord over an attack path in a back path could be an unsafe spot for an overlord, if you’re attacked, but if the information you gain from that overlord dying makes it a worthwhile investment.

The same can be said for Protoss pylons and Terran supply depots. Protoss players should try to build pylons along the edge of their base to help detect drops, scouts, or (in late game scenarios) nydus canals. Terran players can do the same with early supply depots by placing them in the corners of their base so they can see (and hopefully pick off) incoming overlord scouts.

So, how was that? I got this straight from a pro Zerg, my man Destiny. Try do do this in your games guys it so good! Drop us a line if you though this was helpful. Good luck, Have fun.

Just finished walking through the droves of fans at Blizzcon 2010,
after taking a minute to gaze at all the scantily clad girls dressing
as World of Warcraft characters I don’t recognize… I took a minute to
think about what the best part of Friday at Blizzcon was. The clear
winner is the Exhibition Match between SlayersBoxer and Fruitdealer
(history of both the players)

Warning This Is Just My Braindump of What Happened IN The Match, At
This Point it is CLEARLY A Spoiler IF You Want The Excitement Of
Watching The Match

In the first match Slayers Boxer made some very early aggression that
made everyone in the audience think that Fruit Dealer was already a
goner. In his usual fashion he pulled through with JUST enough units
to defend the attack and keep his natural. Did quite a bit of
banelings and kept them at the Xelnaga Watch tower to make sure he
knew when Boxer was pushing out. He quickly took a expansion to the
north and Fruit Dealer was running off three bases just as Slayer got
to his second. The critical point in the game was when FruitDealers
drop tech finished researching. At that point Slayers Boxer had
dropped a Thor on the ledge to start dealing damage to Fruit Dealers
natural. Just in the nick of time Fruit Dealer picks up roaches and
lings to drop on the ledge and save the harassment. At the same time
that Fruit Dealer was defending his natural, he loaded up some
banelings into an overlord and sent it towards Boxers main for a
baneling drop. It was perfect timing and he got two banelings off
with probably a total of 6 or 7 scv’s killed. The crowd went crazy at
this point and was just really excited to see all of this happening.
Boxer continued to pump units and did a fast switch from bio to tech
throwing down three Factories at the same time. This surprised Fruit
Dealer so he was quick to retreat to the Xelnaga watch tower and wait
for Boxer to get out into the open. There was a critical point in
the match where boxer was pushing out and cleverly microing his
marines away from banelings on the way to destroy them (as the roaches
took on his thors in front) at the same time Fruit Dealer brought in
overlords with banelings and bombed right on top of the marines
destroying the bulk of his force. I believe right after this point
Boxer finally gg’d because at that point Fruit Dealer was working on
his 4th expansion and keeping boxer at bay from taking his 3rd. In
the first match Boxer started by trying to place a bunker down and
send a reaper in, there was lots of exciting drone and scv micro play
and finally Boxer got the bunker down and saved his two scv’s inside.
The reaper followed shortly, got inside just as 4 zerglings ran down
the base to take out the bunker. Saved just in the nick of time… once
again in Fruit Dealer fashion.

Second match was on Metalopis an awesome 4 player map. SlayersBoxer
started by building a barracks at the bottom of his ramp rallying
marines towards slayers base. After a initial scout Boxer must have
been grinning because everyone knows that FruitDealer goes 14 hatch,
he loves it. So once boxer saw the hatch with his scout he went for a
quick wall in with two bunkers. The drones at that point could only
hope for an scv to drift to the ramp side of the base or else he would
never get the bunkers in time. Boxers marine came just in time,
pushed back the drones and bunkered up to force Fruit Dealer to cancel
his natural. At this point once again, Slayers Boxer had the lead.
With his cancelled drone Fruit Dealer went for a risky Gold Minerals
expansion. While Boxer luckily scouted this expansion early, he
didn’t have enough units to do anything about it. Fruit dealer
quickly started spreading creep as fast as he could to the west base
where Slayers Boxer was located. In typical Fruit Dealer fashion he
went for a quick third expansion shortly after Slayers scout of his
rich mineral expansion. Somewhere during the game Fruit Dealer
started spreading creep up to the Top Middle Expansion spot, these
creep tumors gave him the game because Boxer never had the ability to
take his 3rd expansion.

So while the game was exciting and a battle the entire time, Fruit
Dealers zealousness for expansions in the first game and excellent
creep spread in the second game really gave him the game.

This is a great match between Brat_OK (a notoriously aggressive terran player) and TheLittleOne (probably the most popular SC2 player out there). A lot of great commentary from Day9 about TheLittleOne’s Zerg play, and a particularly fun watch for anyone who would expect a nutty game from brat_OK. The littleone keeps him in check with tons of little aggressive plays, forcing Brat_OK to pull back units. †

TheLittleOne’s Zerg play Notes:

Make sure when spreading creep tumors to lead with a creeping overlord to let the tumor expand as far as possible.

Get a queen center map, overlord creep, and start dropping creep tumors.

Infestors + zergling/baneling is really effective, fungal growth makes units stay freeze while you hit them with zerglings.

Late game zergling/infestor make sure to have mutas to help fend off drops.

Ghost snipe ability is a terran counter to infestors.

Building: Hatchery

Allows production of: Drone, Queen, Overlord (and all other Zerg units – providing you have the required buildings)
Requires: Drone
Cost: 300 Minerals
Build Time: 100 Seconds
Upgrades to: Lair

*The Hatchery is used to spawn all Zerg units and to receive gathered resources
*The Hatchery periodically spawns 1 Larva every 10 seconds until it has a total of 3 Larva (Larva morph into Zerg units)
* The Hatchery can house up to a total of 19 Larva if you repeatedly use the Queen’s Spawn Larva ability on it
* The Hatchery grows creep which is used to feed nearby Zerg structures (structures will take damage over time if not on creep)
* Creep gives Zerg units a movement speed bonus
* The Hatchery allows the production of Drones
* The Hatchery allows the production of Queens
* The Hatchery allows the production of Overlords

Unit: Drone

Requires: Hatchery
Cost: 50 Minerals
Build Time: 17 Seconds
Supply Cost: 1

*The Drone is a basic worker unit. Used to harvest minerals and vespine gas as well as mutate into structures (Zerg buildings)
*The Drone can attack ground

Unit: Queen

Requires: Hatchery, Spawning Pool
Cost: 150 Minerals
Build Time: 50 Seconds
Supply Cost: 2

*The Queen is a defensive unit that can Spawn Creep Tumors, Spawn Larva and use the Transfusion ability.
*The Queen can attack ground & air
*The Queen is used to help gain control of the map by spreading Creep Tumors (these grow creep & give vision)
*The Queen is used to help increase Zerg productivity by Spawning Larva onto a Hatchery / Lair / Hive
*The Queen is used to heal other Zerg units or buildings for up to 125 health points
*The Queen is strong against harassing units and has a long ranged anti air attack
*The Queen is weak against more than one unit in general (you should not use her in combat unless you have too)

Unit: Overlord

Requires: Hatchery
Cost: 100 Minerals
Build Time: 25 Seconds
Supply Cost: 0
Morphs into: Overseer (Requires Lair)

*The Overlord is a very slow air unit that is unable to attack but raises the maximum number of units available for each one you make
*The Overlord is used for scouting mostly (Especially once you get the Pneumatized Carapace which greatly increases the movement speed of the Overlord)
*The Overlord can also be used to transport units (Requires Ventral Sacs upgrade from the Lair)
*The Overlord can Generate Creep (Requires Lair) which causes Creep to form underneath the Overlord. This ability is best used by spreading your Overlords across the pathways on the map you wish to travel and having them all Generate Creep so your units can move a lot faster across the map. You can also use this ability to build Zerg buildings on, so you can sneak an Overlord to an area on the map that is less likely to be detected by your opponent and build a Spire (for example) so you can get mass air units without him being able to see it coming (unless he detects it of course)

Extractor

Requires: Drone
Cost: 25 Minerals
Build Time: 30 Seconds

*You build the Extractor over a Vespene Geyser in order allow harvesting of the Vespine Gas it contains
*You can get away with avoiding building this early game but if you want to progress onto Mid or Late game you will need the Vespine Gas in order to tech & build better units as well as buildings

Building: Spawning Pool

Allows production of: Zerglings, Queen, Spine Crawlers
Requires: Drone, Hatchery
Cost: 200 Minerals
Build Time: 65 Seconds

*The Spawning Pool can research the upgrade Metabolic Boost (Requires: Hatchery) which Increases the movement speed of Zerglings making them much more efficient at doing their job of harassment & surrounding
*The Spawning Pool can research the upgrade Adrenal Glands (Requires: Lair) which increases the attack speed of Zerglings so they can chew through units & buildings that extra bit faster
*The Spawning Pool allows the production of Zerglings
*The Spawning Pool allows the production of Spine Crawlers

Unit: Zergling (2 Zerglings are created from every Zergling egg that hatches)

Requires: Hatchery, Spawning Pool
Cost: 50 Minerals
Build Time: 24 Seconds
Supply Cost: 1
Morphs into: Baneling (Requires Baneling Nest)

*Zerglings are a speedy melee unit with a very fast attack speed
*Zerglings can attack ground
*Zerglings operate as excellent scouts (very fast and cheap)
*Zerglings are very effective at harassment
*Zerglings can quickly surround enemy units
*Zerglings can morph into Banelings
*Zerglings can be used to prevent your opponent from building if you burrow them underground where they try to build. A great place to burrow a Zergling is at any potential expansion you expect your opponent to take
*Zerglings perform at their best in during the early game but can still prove useful mid game though they tend to start lacking in the late game
*Zerglings are strong against Marauder, Stalker & Hydralisk
*Zerglings are weak against Hellion, Archon & Baneling

Building: Spine Crawler

Requires: Drone, Spawning Pool
Cost: 100 Minerals
Build Time: 50 Seconds
Supply Cost: 0

*Static Defence that attacks ground only
*Can uproot from the ground and move to another position (can only root on creep)
*The Spine Crawler is effective against Hellion harass & small sized armies that lack units which can do bonus damage vs armoured
*The Spine Crawler can be strong at all times of the game due to the flexibility of being able to move them anywhere on the map providing you place creep there
*You can use Spine Crawlers in an offensive manner by sending them close to an enemy base and rooting them nearby with creep

Building: Baneling Nest

Allows production of: Baneling (Ability to Morph a Zergling into a Baneling)
Requires: Drone, Hatchery, Spawning Pool
Cost: 100 Minerals, 50 Vespine Gas
Build Time: 60 Seconds

*The Baneling Nest allows Zerglings the ability to morph into Banelings
*The Baneling Nest is worth getting if you are fighting against many ‘light’ armored units with low health points
*The Baneling Nest can research the upgrade Centrifugal Hooks which increases the movement speed of Banelings giving them a much greater chance of being able to reach their target and blow it up before being

Unit: Baneling

Requires: Zergling (to morph into a Baneling), Hatchery, Baneling Nest
Cost: 25 Minerals, 25 Vespine Gas
Build Time: 20 Seconds
Supply Cost: 0

*The Baneling is a Suicide unit that does damage over a small area
*The Baneling can attack ground
*The Baneling is very effective against tightly packed ‘light’ armoured units with low health points
*The Baneling can be useful at almost any time period of the game
*You can set up traps with your Banelings by burrowing them at certain choke points or places where your enemy is likely to step over them then press X to explode them!
*Great places to set up these traps can be at your Natural Expansion choke point, or a ramp or even along a potential enemy mineral line where he is likely to expand, so when he has sent enough workers to gather minerals there you blow up your Banelings!
*Banelings are strong against Marine, Zealot & Zergling
*Banelings are weak against Thor, Stalker & Roach

Building: Roach Warren

Allows production of: Roach
Requires: Drone, Hatchery, Spawning Pool
Cost: 150 Minerals
Build Time: 55 Seconds

*The Roach Waren can research the upgrade Glial Reconstitution (Requires Lair) which increases the movement speed of Roaches. This is very useful if you are using Roaches to assault the enemy or to defend your base.
*The Roach Warren can research the upgrade Tunneling Claws (Requires Lair) which enables Roaches to move while burrowed. You will need to research the ability Burrow from Lair in order to use this upgrade with Roaches but if you do it can be a fantastic way to sneak up and surprise your enemy as your Roaches become “invisible” when burrowing and can only be seen by detection.
The Roach Warren can research the upgrade Organic Carapace (Requires Hive) which increases the life regeneration rate of burrowed Roaches so once you have researched the ability Burrow you can quickly heal your Roaches whenever you burrow them.

Unit: Roach

Requires: Hatchery, Roach Warren
Cost: 75 Minerals, 25 Vespine Gas
Build Time: 27 Seconds
Supply Cost: 2

*Roaches fulfil a cheap and effective tank role in Starcraft 2
*Roaches can attack ground
*Roaches can take a lot of damage (in comparison to other Zerg units) helping your other units to stay alive that much longer whilst they deal the damage
*Should you need to delay an inevitable attack whilst you tech to stronger units you can help slow your opponent down by blocking tight choke points with Roaches (like the Ramps)
*Roaches also provide a cheap & somewhat effective deterrent against harass units like Hellions or Reapers
*Roaches perform best at mid game, though they can be useful early game if you have enough supply to support them
*Roaches are strong against Hellion, Zealot & Zergling
*Roaches are weak against Marauder, Immortal & Ultralisk

Building: Evolution Chamber

Requires: Drone, Hatchery
Cost: 75 Minerals
Build Time: 35 Seconds

*The Evolution Chamber contains upgrades for Zerg ground units (Increased damage to melee, Increased damage to range & armour upgrades) so obviously if you are focusing on getting a lot of Zerg ground units then you will want to research these upgrades
*The Evolution Chamber is mostly used for Mid to Late game where you will need to increase the damage and armour of your Zerg units if you want them to have more survivability (which they will definitely need from Mid game onwards)
*However, sometimes an early Evolution Chamber can be the difference between you winning or losing. For example, if you are playing Zerg vs Zerg and you both have Zerglings & Banelings BUT you have 1 armor upgrade from the Evolution Chamber then instead of your Zerglings dying to 1 Baneling, they will survive with 1 health point. This can make an incredible difference as your opponent may end up having to use double the amount of banelings per Zergling you have to kill them.

Building: Spore Crawler

Requires: Drone, Evolution Chamber
Cost: 75 Minerals
Build Time: 30 Seconds
Supply Cost: 0

*Static Defence that attacks air only
*Can uproot from the ground and move to another position (can only root on creep)
*The Spore Crawler is effective cloaked Banshees & Dark Templar in particular as it can detect invisible units. It can also detect moving burrowed roaches
*The Spore Crawler is a situational building that most the time is rarely needed
*You can use Spore Crawlers in an offensive manner by sending them close to an enemy base and rooting them nearby with creep

Building: Lair

Allows production of: Drone, Queen, Overlord (and all other Zerg units – providing you have the required buildings)
Requires: Hatchery, Spawning Pool
Cost: 150 Minerals, 150 Vespine Gas
Build Time: 80 Seconds
Upgrades to: Hive

*The Lair is an evolved version of the Hatchery (it has all the same abilities of a Hatchery) but allows for additional upgrades and buildings to be produced.
*Allows the production of Overseers (Ability to Morph an Overlord into an Overseer)
*The Lair can research the ability Burrow which can be used by all Zerg ground units, it also works in conjunction with many of the various upgrades you can get for Zerg units (For example, the upgrade where Roaches can move whilst burrowed)
*The Lair can research the ability Pneumatized Carapace which increases the movement speed of Overlords & Overseers. This is a very cheap and quick upgrade too research and is totally worth it due to the greatly extended vision you can now get with being able to send fast Overlords all over the map to gather vital information. The ability also helps Overlords move out of enemy fire easier.
*The Lair can research the ability Ventral Sacs which allows Overlords to transport units. This ability works great with the other upgrade for Overlords that increases their speed as you can now reliably move ground units about in air space. This ability works extremely effectively with Banelings by dropping the transported Banelings onto enemy Workers or armies

Unit: Overseer

Requires: Overlord (to morph into an Overseer), Lair
Cost: 50 Minerals, 100 Vespine Gas
Build Time: 17 Seconds
Supply Cost: 0

*The Overseer is a fast flying caster harass unit (unable to attack) that acts as a detector should you need to scout for invisible units.
*The Overseer can use the ability Spawn Changeling to create a changeling that you send to places your opponent will be to gather vital Intel on their status (the changeling will change into a Zealot, Marine, or Zergling, depending on the enemy race as it approaches your opponent’s forces).
*The Overseer can use the ability Contaminate to covers an enemy structure in slime preventing it from being able to train units or research upgrades for 30 seconds. This is a useful ability if you want to slow down the production rate of some of the stronger units your opponent may make.
*The Overseer can use the ability Infested Terran to spawn an Infested Terran underneath him that will do up to 100 damage for the 20 seconds that it lasts for, this isn’t all that great but could be useful to place at any of your opponent’s newly built expansions that have a few workers.

Building: Hydralisk Den

Allows production of: Hydralisk
Requires: Drone, Lair
Cost: 100 Minerals, 100 Vespine Gas
Build Time: 40 Seconds

*The Hydralisk Den can research the upgrade Grooved Spines which increases the range of your Hydralisks by 1. This is necessary to allow your Hydralisks to outrange Marines & various other units.

Unit: Hydralisk

Requires: Lair, Hydralisk Den
Cost: 100 Minerals, 50 Vespine Gas
Build Time: 33 Seconds
Supply Cost: 2

*The Hydralisk is the backbone of the Zerg army as they deal fantastic damage to both ground and air with their super fast attack speed (they are also one of the few Zerg units that can actually counter air effectively)
*The Hydralisk can attack ground & air
*The Hydralisk is fragile so you’ll want to keep them behind Roaches
*The Hydralisk is very slow off creep, so the more creep you can spread the better it will be for your Hydralisks
*The Hydralisk performs very well Mid Game and they also do well in Late Game
*Hydralisks are strong against Battlecruiser, Void Ray, Mutalisk
*Hydralisks are weak against Marine, Zealot, Zergling

Building: Infestation Pit

Allows production of: Infestors
Requires: Drone, Lair
Cost: 100 Minerals, 100 Vespine Gas
Build Time: 50 Seconds

*The Infestation Pit can research the upgrade Peristalsis which allows Infestors to move faster while burrowed. This ability is mainly to keep your Infestors safe and to allow them to get into range in a battle to use their abilities instead of them being stuck behind units not being able to do anything.
*The Infestation Pit can research the upgrade Neural Parasite which allows Infestors to control enemy units (best use this on threatening tier 2/3 enemy units). It’s a great ability as it can work on air too. It not only reduces the amount of (potentially) devastating damage you may take but it also allows you to take that damage and turn it around onto your opponent’s army instead.
*The Infestation Pit can research the upgrade Pathogen Glands which increases the Infestors starting energy by 25. This is useful for if you are going to be making a lot of Infestors and you need them now! As soon as they come out of the Hatchery they will be able to use their Fungal Growth ability which is why this upgrade can be so useful.

Unit: Infestor

Requires: Lair, Infestation Pit
Cost: 100 Minerals, 150 Vespine Gas
Build Time: 50 Seconds
Supply Cost: 2

*The Infestor is a caster unit that is unable to attack
*The Infestor is a very useful support unit for the majority of Zerg armies
*The Infestor can use the ability Frenzy to render a friendly unit immune to slows, stuns and mind control & will increase the damage it deals by 25%. This is really an ability specifically designed for the use on the Ultralisk, unless you have Ultralisks you’re better off saving the energy
*The Infestor can use the ability Fungal Growth to immobilise enemy units within the target area of effect and cause 36 damage to them over 8 seconds. This ability works wonders against low health point units like Marines & Workers, it works even better when used with Banelings as they will be able to reach the trapped Marines / Workers and blow them all up! This ability also reveals cloaked and burrowed units so use it if you are suspicious and have the spare energy!
*The Infestor can use the ability Neural Parasite to control a unit it dies or the Infestor relinquishes control. Use this ability on the more threatening units that your opponent might have.
*Infestors are strong against Marine, Colossus, Mutalisk
*Infestors are weak against Ghost

Building: Spire

Allows production of: Mutalisks, Corruptor
Requires: Drone, Lair
Cost: 200 Minerals, 200 Vespine Gas
Build Time: 100 Seconds
Upgrades to: Greater Spire

*The Spire contains upgrades for Zerg air units however these upgrades take a long time to research and I advise you only research these upgrades if you have the time & resources (most likely in a Late Game situation).
*The  Spire can mutate into a Greater Spire (Requires Hive) which is where you can build the best Tier 3 unit Zerg currently has.

Unit: Mutalisk

Requires: Lair, Spire
Cost: 100 Minerals, 100 Vespine Gas
Build Time: 33 Seconds
Supply Cost: 2

*The Mutalisk is an air unit that has great speed and harass capabilities as it bounces its attacks to hit multiple targets so when used against groups of units, Mutalisks can deal devastating overall damage.
*Can attack ground & air
*The Mutalisk is best used as a harassment unit and is particularly effective against Workers or groups of low health point units
*The Mutalisk performs very well at Mid Game and can perform adequately Late Game
*Mutalisks are strong against Viking, Void Ray
*Mutalisks are weak against Marine, Phoenix, Corruptor

Unit: Corruptor

Requires: Lair, Spire
Cost: 150 Minerals, 100 Vespine Gas
Build Time: 40 Seconds
Supply Cost: 2
Mutates into: Brood Lord (Requires Hive)

*The Corruptor is an anti-air flying unit that has the ability to corrupt enemy units, causing them to take more damage.
*Can attack only air
*The Corruptor can use the ability Corruption covers the target unit in acidic spores increasing damage taken by 20% for 30 seconds
*The Corruptor is particularly useful against ‘Massive’ armoured units and is increasingly used more and more in Zerg vs Protoss games in order to counter Colossus as they can be hit by air.
*The Corruptor can morph into a Brood Lord (Requires Hive)
*The Corruptor performs at it’s best towards the Late Game only and even then it is quite situational if your Corruptor will be much use so stick to making Corruptor only if you want to counter ‘Massive’ armoured units
*Corruptors are strong against Phoenix, Battlecruiser, Mutalisk
*Corruptors are weak against Viking, Void Ray

Building: Nydus Network

Needed to produce: Nydus Worm
Requires: Drone, Lair
Build Time: 50 Seconds (20 seconds for each Nydus Worm created from the Nydus Network)
Costs: 150 Minerals, 200 Vespine Gas (100 Minerals, 100 Vespine Gas for each Nydus Worm created from the Nydus Network)

*The Nydus Network is a unique building that is used to transport units between Nydus Worms. It costs 100 Minerals & 100 Vespine Gas per Nydus Worm you create using the Nydus Network. You can spawn a Nydus Worm anywhere on placeable terrain on the map providing you have vision of the area first.
*You should build this building if you want to infiltrate an opponent’s main base or expansion. You can even use it to transport a Drone onto a secluded island on the map that contains minerals & vespine gas and make a Hatchery there.
*This building cannot be created early game, it is useful mid game and performs at its best at late game as you will have more resources to afford enough Nydus Worms thus giving your units more mobility across the map
*The strength of the Nydus Network is that, if undetected, can allow you to cause massive amounts of damage to an opponent should he be able to react in time and kill the forces that you spawn forth from the Nydus Worm. The Nydus Network is also useful for harassing enemy expansions that aren’t so protected, this can have an additional bonus effect of forcing the enemy to pull back his forces in order to have to deal with your harassment assault
*The weakness of the Nydus Network is that it is expensive and takes a long time to build, it also makes a screeching warning sound for your opponent once you have finished creating a Nydus Worm from your Nydus Network regardless of where they are on the map so they are immediately made aware of the Nydus Worm. Also be aware that should your Nydus Worm & Nydus Network be killed whilst carrying units, all of the units inside will die.

Building: Hive

Allows production of: Drone, Queen, Overlord (and all other Zerg units – providing you have the required buildings)
Requires: Lair, Infestation Pit
Cost: 200 Minerals, 150 Vespine Gas
Build Time: 100 Seconds
Upgrades to: Hive

*The Hive is the next step of evolution on from Lair (it has all the same abilities of a Lair) but allows for additional upgrades and buildings to be produced.

Building: Ultralisk Cavern

Allows production of: Ultralisk
Requires: Drone, Hive
Cost: 150 Minerals, 200 Vespine Gas
Build Time: 65 Seconds

*The Ultralisk Cavern can research the upgrade Anabolic Synthesis which increases the movement speed of Ultralisks. If you are going to invest this many resources into getting Ultralisks then I heavily suggest you get this upgrade otherwise Ultralisks move far too slowly to be effective.
*The Ultralisk Cavern can research the upgrade Chitinous Plating which gives +2 armour to Ultralisks. Once again I advise you to also get this upgrade due to the amount of upgrades you need to make in order for the Ultralisk to be useful.

Unit: Ultralisk

Requires: Hive, Ultralisk Cavern
Cost: 300 Minerals, 200 Vespine Gas
Build Time: 70 Seconds
Supply Cost: 6

*The Ultralisk is a heavy assault beast with an area damage attack.
*Can attack ground
*The Ultralisk is meant to be the tank of the Zerg unit that charges into battle taking the damage & covering for the more fragile Zerg units that should follow closely behind
*The Ultralisk can be used effectively against ‘Light’ armoured units but suffers greatly against most ‘Armoured’ units as many ‘Armoured’ units deal a lot of bonus damage vs other ‘armoured’ units and it’s because of this Ultralisks die too quickly before they can even get close
*The Ultralisk is not very efficient in terms of damage for cost, even though he is a Tier 3 unit & I suggest you avoid making an Ultralisk unless it seems like he will be the perfect counter to your opponent.
*Ultralisks are strong against Marine, Zealot, Zergling
*Ultralisks are weak against Marauder, Immortal

Building: Greater Spire

Allows production of: Brood Lord
Requires: Hive, Spire (to mutate into a Greater Spire)
Cost: 100 Minerals, 150 Vespine Gas
Build Time: 100 Seconds

*The Greater Spire now allows Corruptors the ability to morph in Brood Lords.

Unit: Brood Lord

Requires: Greater Spire
Cost: 150 Minerals, 150 Vespine Gas
Build Time: 34 Seconds
Supply Cost: 2

*The Brood Lord is an anti-ground (unable to attack air) heavy assault unit that shoots broodlings at its target
*The Brood Lord is incredibly slow and must be positioned over high cliff tops if possible so as to avoid being targeted by ground anti air units
*The Brood Lord acts as the only long range Siege unit that Zerg have and is best used in that way, with a massive 9.5 range you should keep the Brood Lord at the furthest possible attacking range from your enemy at all times
*You need to focus on protecting your Brood Lord at all costs as it is the key to securing Late Game victories
*The Brood Lord does initial damage to its target and on top of this he spawns 2 broodlings each time he attacks
*Broodlings are like slightly weaker Zerglings and last a short limited time however they can be very effective as they are essentially free units so the more your enemy wastes his firepower and units on them the better
*Each Brood Lord can spawn up to 6 Broodlings on a target enemy unit before the first 2 it spawned expire
*The Brood Lord is without doubt the best Tier 3 Zerg unit and is worth the expensive tech in most circumstances as it plays a vital role in Late Game
*Brood Lords are strong against Stalker
*Brood Lords are weak against Viking, Void Ray, Corruptor

Starcraft-2-Zerg-12-Pool-Speedling-Rush-Strategy

Overview

The 12 Pool Speedling Push is a more reliable form of overwhelming your opponent with Zerglings whilst maintaining a satisfactory economy. This strategy can be played out in several ways, you may want to constantly send Zerglings in small groups as they spawn straight to your opponent or you can save them all up and attack with up to 20 Speedlings all in one huge group.

The purpose of the 12 Pool Speedling Push ideally is to surprise your opponent with 20 Speedlings however you can consistently harass your opponent as your Zerglings spawn if you prefer. The idea behind 12 Pool Speedling Push is really to make a huge group of Zerglings all at roughly the same time with the help of the Spawn Larva ability and catch your opponent off guard. This can be achieved quite successfully as long as you prevent your opponent from properly scouting or seeing anymore then just 2 Zerglings then they will not be ready for when you spawn almost all of your Zergling army in one go. By the time you hit your opponent with your group of 20 Speedlings it will be too late for them to react accordingly.

Build order

This build order is designed as a straight forward build to forming the strategy, it does not consider any of the multiple various enemy threats that you may encounter. You should only deviate away from the build order to build appropriate counters (an army or static defence) should your opponent threaten your survivability. Try to stick to the build order as best as you can to achieve maximum results.

*Text in BOLD CAPITAL letters – refers to units & buildings that you will build.
*Text in Italics - refers to what action you need to take with the unit or building)
*Text in underline – refers to a mechanic or ability you need to use.

1. DRONE
2. DRONE
3. DRONE
4. DRONE
5. Gather 150 minerals & build 2 EXTRACTORS
6. DRONE
7. DRONE
8. Cancel the 2 Extractors that you built & send the Drones back onto minerals(This is known as the Extractor Trick, see the “Macro” section for a clarification on the purpose of the Extractor Trick)
9. Send a Drone to scout for the enemy base
10. OVERLORD
11. EXTRACTOR
12. SPAWNING POOL
13. Gather 75 minerals & build an EXTRACTOR
14. Cancel the second Extractor (make sure you don’t cancel the first Extractor you built)
15. DRONE
16. DRONE
17. DRONE
18. QUEEN
19. ZERGLING (These Zerglings are built with the main priority of killing any enemy scouts. After that the Zerglings purpose is to scout& harass – first scout your main and natural expansion area quickly, then send one of each of the two zerglings to each Xel Naga Tower, then scout the enemy base as you see appropriate with either one or both of the zerglings. When you are satisfied with your scouting/harass you can either keep a zergling just outside by their natural expansion to keep a check on your opponent or bring it back to the xel naga tower nearest your enemy)
20. DRONE
21. METABOLIC BOOST (Research at Spawning Pool)
22. Take all 3 Drones from the Extractor and put them onto minerals
23. OVERLORD
24. ZERGLING
25. The Queen you built at your Main Hatchery will spawn(Use her Spawn Larva ability on your Main Hatchery – Use this ability every 40 seconds from now on)
26. ZERGLING
27. ZERGLING
28. ZERGLING
29. ZERGLING
30. ZERGLING x4
31. OVERLORD

*From this point on you need to build in reaction to how your opponent is playing (See “Play style“). If you would like some suggestions then you could continue onwards using either of these:

[a] Continue massing Zerglings (If your opponent can be easily outnumbered & overwhelmed)
[b] Continue making Zerglings & an Expansion (If you can do good damage to your opponent but are unable to finish them off)
[c] Put 3 Drones back onto an Extractor & build a Baneling Nest whilst continuing to make Zerglings so you can eventually morph them into Banelings – Maybe take a 2nd Extractor to ensure you have enough Vespine Gas (If your opponent is focusing on creating ‘Light’ armoured units – also for blowing up workers)
[d] Start making Drones (if there is no way you can beat your opponent so you can boost your economy and prepare for a longer game)

Play style

With a 12 Pool Speedling Push you want to surprise your opponent with a large group of up to 20 Speedlings at once. If you follow the build order closely then you will finish researching Metabolic Boost by the time your last lot of Zerglings spawn from your Hatchery, this will give you an immense advantage if you are able to get inside your opponent’s base as the speed will make it very hard for your opponent to control you effectively.

You need to focus on killing enemy workers or buildings that will help slow down the enemy production rate (such as Pylons). You will increase your chances of winning a great deal more by killing workers over army units as this will slow down the enemy economy and do greater overall damage. The other reason for focusing enemy workers over army units with your Zerglings is that should the rush become stoppable by your opponent then at least you will have slowed down their economy enough to reduce their ability to outnumber you with units.

This strategy is dependent upon tricking your opponent into thinking you are no threat early game & refusing them access and sight of your main base (Especially when you are about to make a ton of Zerglings at once with Spawn Larva or if you decide to build a Baneling Nest). If your opponent scouts you mass producing Zerglings or a Baneling Nest then he will have precious extra time to create counters like Photon Cannons, Sentries (for Force Field) or Chrono Boost (to mass produce an army) so it is crucial you keep your opponent in the dark and keep them thinking you are not a threat for the time being.

Using only a couple of Zerglings to harass and then backing off when they respond to the harass will help fool your opponent and mislead them into thinking they has control of the situation (hopefully they will decide to put extra resources into tech should they feel you aren’t a threat) giving you the perfect opportunity to overwhelm them with Speedlings in one huge push later on.

Micro

*Focus on killing workers with your Zerglings
*Hit and run the workers; Attack the workers with your Zerglings and provoke your opponent into dragging all of his workers away from the mineral line to defend himself, at this point you simply run your Zerglings back and wait for him to return his workers to the mineral line, that’s when you strike again with the Zerglings! Rinse & repeat this method whenever possible. This allows you to efficiently damage your opponent’s economy whilst taking as little damage as possible.
*Kill the enemy army units only if you can still put the pressure on after inevitably losing some Zerglings in the process otherwise dodge the enemy army units and harass their workers instead.
*kill any key buildings like Pylons should you have the chance (Especially if there is only Pylon powering Protoss buildings)
*See “Support” for advice on how to use Banelings if you have the chance to make them

Macro

*Spawn Larva whenever possible to increase the number of Zerglings you can create
*Start spawning Creep Tumors only once your Queen has enough energy to continually Spawn Larva first
*The “Extractor Trick” is a method Zerg players use to temporarily exceed their supply limit so they can build a extra Drones or Zerglings before needing to make an Overlord

Upgrades

This is a list of the preferred upgrades for this strategy should you have the chance to research them.
[Some of the upgrades further down the list may be not be necessary depending upon the units & playstyle you choose to use]

1. Metabolic Boost (Increases the movement speed of Zerglings)
[Requires: Hatchery, Spawning Pool]
This is an exceptional ability that will boost the effectiveness of your Zerglings greatly. They will move much faster and will be able to perform hit and run attacks on workers whilst being able to dodge enemy army units with much more ease. You will gain a lot more control with this upgrade allowing you to really put the pressure on your opponent.

2. Evolve Centrifugal Hooks (Increases the movement speed of all Banelings)
[Requires: Hatchery, Baneling Nest]
This greatly improves your Banelings ability to surprise your opponents army without losing so much.

3. Evolve Burrow (Enables all Zerg ground units to burrow making it invisible unless detected)
[Requires: Lair]
This ability is useful for both Zerglings and Banelings in particular. Burrowed Zerglings, if placed carefully, will prevent your opponent from building on the same spot you have burrowed that Zergling. I suggest using this ability with Zerglings at places you expect your opponent to build (like expansion areas) so he will need to go to the effort of detecting your Zergling and killing it before he can build anything.

Burrowed Banelings can act as land mines because you are able to explode them whilst they are burrowed. This can be absolutely devastating if used correctly. The best way to use burrowed Banelings is to spread them out across choke points (most likely your own natural expansion choke point) and wait for your opponent to march his army right over them then highlight the ones in range of his army and press X to explode the Banelings. You can also use burrowed Banelings as a pre-emptive strike, for example, if you suspect your opponent is going to expand then you can burrow several banelings along the gap in between where his expansion and the mineral line is. Then you wait for the appropriate time (preferably when the mineral line is fully saturated with workers) and blow up all of his workers at once. In both cases I suggest you use Banelings in situations where they are unlikely to be detected or if your opponent puts little effort into scouting and detecting.

4. Pneumatized Carapace (Increases the movement speed of Overlords and Overseers)
[Requires: Lair]
This is necessary as you will need to keep checks on your opponent so you can build units/buildings in accordance to how he is playing. Using your Overlords with this upgrade allows you to scout with multiple moderately fast air units (Overlords) which will give you a larger scope of what is happening on the map.

Support

The only unit that you will be able to realistically build to assist with this Strategy will be the Baneling, if you are able to create anymore units then it is likely you are going to be playing a longer game than the strategy intends.

*Use Banelings to deal great area of effect damage to ‘light’ armoured units such as Probes or Zealots
*You may need Banelings to bust into your opponents base should he be blocking his ramp with buildings or Zealots at a Choke point

Protoss

1. Proxy Rush
2. 2 Gateway Push
3. 4 Gateway Push
4. 3 Gateway 1 Robotics Push
5. Mass Stalker (Tech & Play)
6. Fast Void Ray Rush
7. Collosus Tech Rush
8.High Templar Tech Rush
9. Dark Templar Tech Rush
10. Warp Prism Harassment Techniques

Terran

1. MMM Bio Ball
2. Hellion Harass
3. Fast Marine & Siege Tank Push
4. Fast Banshee Rush
5. Lift-Off Defence (This involves lifting your command center on certain maps to an expansion blocked by destructable rocks
6. Thor Drop
7. Reaper Rush
8. Marine & Bunker Push
9. Invisible Ghost Nuke Rush
10. 3 Barracks Marauder Rush

Zerg

1. MutaLisk
2. Roachalisk
3. 12 Pool Speedling Push
4. 6 Pool Zergling Rush
5. Fast Roaches
6. Fast Hydralisks
7. Standard Expansion Build
8. Brood Lord build
9. Baneling Bust
10. Nydus Worm Techniques

The Protoss are a highly developed race with advanced technology and potent psionic abilities. They believed they were the strongest species but those beliefs have been shattered as a result of their war with the Zerg. Even the most powerful of the Protoss race have succumbed to the overwhelming mass of the Zerg Swarm. The Protoss have built their society around core philosophies that have been strictly studied and followed for over a millennium.

The Protoss  have been stubborn in their misplaced confidence of their own superiority over all other life and have learnt a painful but valuable lesson after suffering so many tragic unavoidable losses. The zerg invasion of the Protoss homeworld, Aiur, has taken the Protoss race to a crisis point where they must make a defining change to their way of life if they want to survive and overcome the challenges that await them. New technology and strategies are being developed in the desperate struggle to fight the Zerg. Even long forgotten weapons that were cast aside are now being reconsidered as the Protoss establish all efforts in a bid to continue the existence of their noble race.

Unlike the Zerg, the Protoss lack an abundance of soldiers. The Protoss have conventionally sustained their numbers by using a mixture of robotic war machines to help support their forces. Protoss warriors dedicate themselves vigorously to the art of combat and combine cybernetic technology with their psionic abilities to become formidable fighting machines. Whilst Protoss warriors are fearsome, the utmost strength of Protoss rests in the supremacy of their Space armada. The Protoss are honourable fighters but they must fight with mobility, stealth and surprise in order to preserve their population and continue to fight against their nemesis, the Zerg.

A great build for Terran against the Zerg race is a mechanized build.  Siege Tanks, and especially Thors are powerful against the Zerg.  Hellions also do a great job of harassment since Zerg players have a harder time of walling off the entrance points to their bases.  In this section a standard build order against the Zerg will be explained in detail.  At the end of the detailed breakdown, there will be a “quick reference list” for you to follow along quickly during your first few games using this build.  It is important to always remember that everything in Starcraft 2 has a hard counter, so always stay on top of scouting and ensure your opponent will not be throwing you any surprises.  If you see your opponent specifically countering what you are doing, be ready to diversify your army and transition into another build.

Getting Started:  Standard opening up to your first Barracks and Facotry.

When the game starts, the first thing you should do is start building an SCV out of your Command Center, and then immediately move all of your SCVs to mine minerals.  If you are fast enough, try splitting your SCVs and sending 3 to one mineral node, and 3 to another.  By doing that they will split faster between six different mineral nodes than if you had of commanded all 6 to go to one and let them automatically split up from there.

Now hotkey your Command Center to a number you feel comfortable with (hold down Control and press a number).  Build another SCV as soon as you are able.  Keep building SCVs for the next couple moments.  Watch your supply count at the top right corner of the screen.  When you are at 9, get ready to make another action.  The second your supply counter hits 10, grab that SCV that just spawned from your Command Center (this is technically your 9^th SCV as your 10^th is currently being made), move it to the ramp of your base and build a supply depot as soon as you are able.  The timing should work out perfectly that you can throw that supply depot down right away.  Note that walling off your base is important against a Zerg player to prevent Zerglings from running in and surrounding your marines early on, and to prevent the Zerglings from reaching your mineral line and destroying your precious SCVs.

Queue up another SCV while your Supply Depot is being built.  Once your 11^th SCV is made, you will not be able to make more until the Supply Depot finishes, so you do not need to worry about queuing up any more after your 11^th.  The second your Supply Depot finishes, using the same SCV that made it, build a Barracks right beside it.  The idea is to wall your ramp off using a Supply Depot (sometimes two are necessary) and the Barracks.  Be sure there is sufficient space to the right of your Barracks for an add-on to be made.  Not leaving enough space for an add-on will mean it will have to lift-off and move, and you will waste precious time.

While your Barracks is being built, queue up one SCV.  Then, once you have enough minerals, use one of your mining SCVs to build a Refinery.  Once the Refinery starts being built, just keep queuing SCVs with all your remaining minerals.  Your Refinery will complete before your Barracks.  Once it is complete, move two more SCVs from your mineral line to mine gas from the Refinery.  Keep queuing SCVs until your Barracks finishes.  Try to leave 50-150 minerals for when your Barracks completes.  The instant your Barracks is complete, produce one Marine from it.  Now send the SCV that made your Barracks out to scout your opponent.  Hotkey it so you can snap your view to it instantly once it arrives in your opponent’s base.  Set a rally point for your Barracks behind your wall but close enough to the ramp that it will be able to shoot any zerglings that attempt to attack or scout your base.

Note that a Drone scout might slip in before your wall gets up, and it might try to be a nuisance and attack the SCV making your Barracks.  If this happens, move an SCV off of your mineral line to attack the Drone.  This will prevent the Drone from killing your SCV on your Barracks.  If you have to, temporarily halt construction on your Barracks to move the injured SCV away and replace it with another undamaged one.  Try not to delay your Barracks if possible!

Now that your Barracks is complete and your scout is on it’s way, use an SCV from the mineral line to build another supply depot.  If your ramp will be walled once the Barrack’s add-on is made, build the supply depot somewhere around the perimeter of your base, so eventually you are viewing your entire base at all times.  If the add-on from the Barracks will not make a tight wall, then place your second supply depot at the ramp.  Also, keep queuing SCVs while your Marine and second supply depot are being built.

Once your marine is produced, throw down a Reactor Core add-on for your Barracks.  Since you started mining gas before the Barracks was even complete, you should easily be able to afford the 50 gas necessary to do this.  Stop queuing SCVs now and once you have 150 minerals upgrade your Command Center to an Orbital Command.  This is important to do early on because each Mule will bring in approximately 300 extra minerals.  Note that the reason you get your Marine before the add-on is for a couple reasons: 1) it gives you at least one unit to thwart away early Zergling pushes of 6 Zerglings at your ramp.  And 2) can be used to shoot at and hunt any Overlords that are scouting your base.

Now your scouting SCV should be in your opponent’s base.  What have you discovered?  Are they Fast Expanding?  Are they going to rush you?  Are they teching into a Lair for Hydras/Mutalisks or are they building a Roach Warren or Baneling Nest?  If they are preparing for a really early Zergling rush, or getting early Banelings to attempt to break down your wall, it may be beneficial to build a Bunker near your wall/ramp for extra defence.  Remember to repair it with SCVs if the Zerg player does attack unusually early.  If they never end up attacking, you can always salvage your Bunker later on and get your 100 minerals back.  If the Zerg player is Fast Expanding (most common), or teching up to Roaches/Hydras/Mutalisks, you can continue this build as normal.

After your Reactor Core finishes, once you have 100 gas, throw down your Factory right away (make sure you also have the 150 minerals required as well).  Once you throw down your Factory, build your second Refinery immediately.  Once that finishes, be sure to put 2 SCVs into it right away.  In the meantime use your Orbital Command to make Mules.  Never scan with your first 50 energy.  If your scout somehow fails at aquiring any information, send another one instead.  Always remember to keep building SCVs as it takes approximately 2-3 SCVs per mineral node for full saturation.  Even if you are fully saturating all mineral nodes, once you expand you can send your excess SCVs to your expansion to start mining right away.  Use any extra minerals while your factory is building to produce Marines and any needed Supply Depots.  Be careful not to Supply Block yourself.  Do not spend any gas while your factory is being built.  You are saving it up for a Siege Tank.

Once your Factory completes, build a Tech Lab add-on right away.  At this point you should have both of your refineries up and running with three SCVs mining from each, and a decent amount of SCVs mining minerals as well.  You should also have at least 3 Marines.

Once the Tech Lab has completed immediately start building your first Siege Tank.  Don’t forget to set a rally point for your Factory, preferably near your ramp.  Right after your Seige Tank begins production, research Siege Mode Upgrade from the Tech Lab as soon as you can.  Spend any extra minerals on Marines.  You should have extra minerals since you gain minerals much faster than gas.  Also, don’t forget to keep building SCVs and Supply Depots!

Once your first Siege Tank is complete, build a second one.  You should be able to queue your second Siege Tank right before your first one finishes, so that production begins immediately.  Keep spending excess minerals on Marines.

Timing Attack:

The instant your second Siege Tank is completed, now is the time to attack the Zerg player!  If timed right, your Siege Mode Upgrade should also be complete, or be complete by the time your army arrives at the Zerg Player’s base.  Usually at this stage, if they Fast Expanded they will only have a few Zerglings, maybe one or two Spine Crawlers.  Perhaps they will have a very small amount of Roaches.  If they teched to Hydralisks or Mutalisks they should have none, or very few out.  If they went for Banelings, keep your Siege Tanks in front of your marines as they can take a hammering of Banelings.

Group your Siege Tanks to a number you feel comfortable with, and group your Marines to a separate number.  Lower your Supply Depot(s) blocking your ramp and move your army out towards the Zerg Player’s base.  Always remember to raise your lowered Supply Depot back up so no Zerg units can sneak into your base!  While moving out across the map keep an eye on your army to make sure they are not being engaged.  Try to keep the Marines in front of the Tanks, unless your opponent went for Banelings, then keep the Siege Tanks in front.

Once you arrive at your opponent’s base (or perhaps their natural expansion), Siege Mode your Tanks before engaging the Zerg player’s army.  If possible, Siege them within range of the Hatchery, or any other building (such as Spine Crawlers).  Your tanks can outrange the Spine Crawlers, so if there are any, make sure you have Sieged up your tanks in range to attack them, but out of range of their attacks.  Keep your Marines really close to your Tanks to prevent Zerglings from getting a surround on your tanks.

Don’t forget to keep building at your base.  Once you start moving out, save up for a Command Center and start building that, inside your base if you like, where it will remain protected, and can then lift off after completion and fly to your natural expansion area.  Once the Command Center starts being build, spend all extra minerals and gas on more Tanks and Marines.  You will need these units in case your attack fails and the Zerg player chooses to counter attack, or in case your attack is somewhat succeeding and requires the reinforcements.

While attacking the Zerg player, if you do not think you have enough forces to destroy their Hatchery, target the workers instead.  Assuming you have disposed of their army (and they are now panicking and building tons of Zerglings/Roaches out of their larvae).  If they have an army, target it first.  Protect your Seige Tanks as best you can since they are the key factor in this early attack.  If all of your marines go down, prepare to unseige your tanks in case Zerglings try to run up for a surround.  If the attack is going poorly, you can always retreat back to your base.  It is always better to fall back if you are unsure, and save your units for a future attack/defence than to waste them and accomplish little!

After your Natural Expansion is up and running:

Once your Command Center has completed being built, if it is safe to do so, fly it to your Natural Expansion location and transfer some of your SCVs from your main base to mine minerals at your expansion.  Move your marines up to the Command Center since this is now where you will have to start defending from.  You may or may not have to move your siege tanks up depending on the map.  They may be better positioned on the high ground in your main base behind your ramp’s wall in Siege Mode.  Upgrade your Command Center into an Orbital Command so now you will have two Orbital Commands for twice the amount of Mules, or even Scans as necessary for occasional scouting.  It is a good idea to keep an SCV or Marine at any watchtowers throughout the map so you maintain a good field of vision of the map at all times.  It is also a good idea to occasional scout the gold high yield mineral locations if there are any, to ensure the Zerg player is not expanding further.

Once your expansion is up and running, build two more Factorys and an Armoury.  This will allow you to start making Thors.  Keep producing Marines, Supply Depots, and SCVs with your remaining minerals.  Also, be sure to build two more Refinerys at your expansion as soon as you are safely able to do so.

Since this point in the game can be considered mid-late stage, it is hard to continue giving exact build order instructions since many variable situations could have or currently be occurring, such as harassment, constant attacks against you, weird tech choices by the Zerg player, etc.  So here is an idea of some things you can build towards and always be sure to constantly scout the Zerg player to see when they are going to attack, when they are expanding again, and what units they are mainly building.

Thors are extremely effective against Mutalisks and fairly good against Hydralisks.  So you can safely produce a lot of Thors out of 3-5 Factories and mix in a few Marines to help with Zerglings and Roaches.  You can also always have a few Siege Tanks mixed in with your Thors, but mainly focusing on Thors at this point in the game is important.  Be sure to get their upgrade since it will allow you to quickly shoot down large units (like the ultralisk), or destroy Hatcheries and other buildings extremely quickly.  Also remember to upgrade weapons and armour at your Armoury!  Upgrades in Starcraft 2 are very important and you can win or lose fights sometimes just because of upgrades!

If the Zerg player is massing a lot of Infestors to counter your Thors (by mind controlling them in combat), try to focus fire them down.  Do not attack your own units unless absolutely necessary.  Killing the Infestor frees your unit.  You can also bring SCVs to your fights to repair the Thors during battle.  If your opponent goes for a heavy Roach build, they are fairly effective against Thors, so be sure to mix some marines in with your army to melt away those Roaches faster.

You can also get a Starport once you feel comfortable and get Vikings for Overlord hunting and try to Supply Cap your Zerg opponent.  Or you can get Ravens, upgrade the Hunter Seeker Missile ability which is incredibly effective against mass Hydralisks and mass Mutalisks.

When you need to expand again, it can be a good idea to go for the high yield gold mineral resources.  It is also a good idea to build a Planetary Fortress with your Command Center since two Orbital Command centers is sufficient for Mule/Scan production and the Planetary Fortress is very effective against Zerg ground units.  Try not to get out expanded by the Zerg.  If they are trying to constantly expand, either equally expand, or pressure them constantly with attacks.  If your Planetary Fortress is under attack, use all SCVs in the area to repair it at once, this will make it very difficult for ground units to destroy.  Also be sure to place turrets around your mineral line at all expansions since Planetary Fortresses cannot attack air, and Mutalisk harassment is fairly common.

If the Zerg player starts getting Broodlords try to focus them down with your Thors, rather than attacking the Broodlings.  Also, build Vikings as a very effective counter to the Broodlord.

Build Order Quick Reference:

• Build your first Supply Depot at 10 Supply Count, and wall off your ramp.
• Build your Barracks immediately after your first Supply Depot, also contributing towards walling off your ramp.
• Build a Refinery while your Barracks is being built.  Put two SCVs into it once it is complete for maximum gas mining.
• Build a Marine and another Supply Depot once your Barracks finishes.  Scout your opponent!
• Upgrade your Command Center to an Orbital Command
• Build a Reactor Core add-on for your Barracks once the first Marine is complete
• Build a Factory as soon as you have the gas
• Build your second Refinery, be sure to put two SCVs into it upon completion for maximum gas mining
• Keep building SCVs, Marines, and Supply Depots with excess minerals
• Build a Tech Lab add-on to your Factory once it is complete
• Build a Siege Tank as soon as your Tech Lab completes
• Research Siege Mode upgrade once your first Siege Tank is being built
• Queue a second Siege Tank up before your first one completes
• Push out once you have two Siege Tanks and a few Marines and the Siege Mode upgrade.  This is also a good time to start your first Expansion.
• Build two more Factorys and an Armoury to transition into Thors
• Upgrade vehicle weapons at your Armoury
• Attack with mass Thors and Marines, perhaps mix a couple Siege Tanks in as well
• Get a Starport and Vikings or Ravens (with Hunter Seeker Missile)
• Expand again once you feel comfortable.  Keep scouting your opponent and keep constant pressure.  Build a Planetary Fortress at your second expansion and beyond.

Good luck and have fun!