Basics
There are two ways to win 2v2:
1) Win
2) Not lose
What I mean by this is at the very core of it, the best 2v2 players are good at both playing aggressively to win the game and defending against the more aggressive players to emerge with an advantage. The easiest way to get ladder points (with a random partner) is to get balanced at doing both, but if you have a teammate, find yourself a sick little cheese and I’ll see you in the Master league! An important thing to note, if you make an attack and fail miserably, or you get killed by a cannon rush, don’t leave!! Your teammate will very likely be ahead, and can potentially carry you to victory. Likewise, if your teammate dies really early, instead of flaming them, you can use your tech/economic advantage to steal a win from some complacent opponents!
Scouting/map control
Figuring out a plan of attack is very important, and knowing what to do is clearly based off of scouting. Everyone in SC2 knows this, but in 2v2, things get a little more interesting. You can commit to hellions/reapers/zerglings/phoenix a lot harder than you can in 1v1 because your teammate is there to make sure you don’t die to some deathpush (bio/roaches/blink stalkers) counterattack. As a result, BUILD THESE UNITS! The units I just mentioned are very strong at claiming map control and scouting what your opponents are doing (not to mention doing damage). Now lets get into what you are looking for with your scouts.
First and foremost, count bases. If you and your teammate have more bases than your opponents, literally do nothing except make units and defend your base. If you see that you and your teammate have 4 bases while your opponents have 3, politely tell your teammate that nydusing or blinking into the enemy base alone is not what you want to be doing. Typically you are going to get allin-ed and you should buckle up for a bumpy one. Making units for defense will allow you to deny expansions that your opponents attempt if they don’t allin you, and you have used your economic edge. If you are behind on bases, figure out a way that you are ahead, and try to abuse that advantage. For example, if your opponents expanded while you were teching to Dark Templar, you could send a dt to each base while expanding aggressively yourself.
Counting gases and looking for tech trees is also important, knowing the tech path of your opponent is very helpful in preparing your attack/defense. The amount of times I have died to DTs is depressing enough as it is, and I would not wish that upon anyone. As you improve, reading gases will become more important, but I think that I shouldn’t get into that in this guide.
Race combos
What makes 2v2 so interesting to me is that there are many many more unit compositions and situations to get in because of twice the number of players. Generally speaking, I find a team with two different races has a lot more options for winning/not losing than TT, PP, or ZZ teams, but there are some important things to know about those combos.
TT:
Reaper builds of the 2 and 3 rax variety are pretty powerful, and having 2 people do them at the same time is very tough to deal with, especially on separated-base maps. Defending this is really really hard, but with tanks, photon overcharge, and spine crawlers in good locations, the reapers should have a tough time finding an opening.
Other than the reaper openings, TT has a very strong option in going bio/mech with one person on each role. Upgrades are very strong, and streamlining your composition allows for some nasty timing pushes with lots of tanks protected by bio.
ZZ:
ZZ is strongest I find in the lategame, with Ultra/Broodlord/Infestor/Viper supported by a few roaches and hydras. This kind of composition is very efficient, and very hard to kill. ZZ can also do a muta/ling/bane player supporting a roach/hydra/lurker player, which is a good way to get to this monstrous lategame composition. I find ZZ tends to be weakest in the midgame, often just dying to 4 or 5 base pushes.
PP:
PP is a tough race combination to read, as they have lots of build options. Between the cannon rushes and proxy stargates and the dt rushes and the safe robo plays, it is often hard to figure out what a protoss player will do, and to make matters worse, there are two of them. Most of the attacks are gateway-centered armies though, with blink stalkers and adepts with the occasional void ray or immortal. Bio and Hydras are always good, and because zealots are no longer commonplace, tanks can be very strong as well.
TZ:
Two words baby: Hellion Ling. This combo has dominated 2v2 since WoL, and is still very strong. No matter what matchup the TZ combo is facing, hellion ling is very good. Not only is it particularly strong at forcing 2v1 situations, it is a strong unit composition that allows for the terran player to get Vikings, Banshees, or Liberators based off of what the situation calls for. Vikings are great at shutting down drops, oracles, or banshees while the hellion ling wins you the game, but banshees are good if your opponents are on lower tech, like roaches or bio.
TP:
TP has a very strong low-economy option for winning games early with a tank/voidray push. The terran player goes for a 1-1-1 reactor barracks marine tank push with either banshees or medivacs while the protoss makes as many voidrays as their little heart can take. Using all of the units to defend the tanks, this (typically 3 base- protoss expands) allin is not only a strong timing push, but great at turtling if the push fails, and you need to try to expand out of it. Mech/airtoss is a great deathball that is very akin to the ZZ lategame deathball in that it is remarkably efficient and only beaten by smart counterattacks and aggressive expansion.
PZ:
PZ can get very aggressive very early with zergling/stalker pushes with a probe and mothership core for more aggressive photon overcharges. This push can be very strong and hard to deal with without a good sim city or static defenses. In the mid and lategame, PZ typically plays passively to amass their own lategame deathball, whichever tech paths each player goes.
These unit compositions and strategies are my opinion of the strongest options that each race combo has based off of playing a lot of the highest level of 2v2. I would love suggestions, and if anyone would like to talk me up or watch replays/my gameplay, shoot me a message or come by my stream at twitch.tv/thecombro.
Thanks for reading!