Mines, and lots of them. Just spam them everywhere... vents, everything. Until hive2, at which point you know you screwed up because they somehow managed to get a hive.
Also, lame up choke points like mad. It'll piss off aliens to no end, and keep you from losing (on occasion).
Btw, don't take anything from this post as serious, cuz i R nub comm lol!!1!!one!1!11!!