4. Ditch team building gimmicks (see #3 for what's important).
I'd say gimmicks aren't going to save you, but consider morale events and other subtler stuff to help build team cohesion. Things like going to lunch regularly together, for example. When people are more comfortable with each other it makes it a lot easier for them to collaborate, rely on each other, ask each other questions, mentor each other, etc.
The art is to distinguish between gimmicks and effective team building. I believe regular lunch together is great. Having a day-long team building event not so much. Watching a movie together is nearly useless because there is little interaction.
I think the important aspect is for people to interact in different contexts. Lunch is already different to the usual office context. Playing games is great in general (board games, paintball, rpg, team sports, whatever).
