I've been a fan of facing the door ever since I read about it in Feng Shui. Basically the idea is that if you can see (even from the corner of your eye) all of the places from which an attacker might come, you can have greater peace of mind. You should try to sit such that you can see any of the doors and windows in your office. Obviously this can be difficult, but I've found that the effort of thinking about it has been worth it.

Coworkers and attackers are pretty much the same thing in the office setting.