For example, did you know that it's possible for 4 Zerglings to beat 4 Zerglings with 3 Zerglings left over, if you micro yours and the opponent doesn't? I still have to learn the trick, but it involves moving your almost-dead Zergling away for a second, and then coming back to gang up on another Zergling. It's a version of focus-fire, but you can't target just one Zergling with all 4 of yours, or you'll spend too much time moving and not enough time attacking. It's very tough to do.
Aggression is normally good in 2v2. However, what I have to learn is NOT to throw units away doing it. It's often not worth it, either because either:
- You force your opponent to go all-in, and after losing your harassment units, he'll have more army than you and roll you over, or
- You don't actually do as much damage with your harassment as it cost you to make the units!
And remember: if you're getting stomped, sometimes it's just better to stop playing for awhile rather than lose, lose and lose some more. Go play the AI a bit, and you may figure out what the problem is.