I tend to leave unarmed players alone. By the time they find a gun, I'll probably be long gone, anyway. Armed players, however, are a much different story. I attempt to avoid shooting on sight as much as possible, even if they have gear worth taking. I find that having a teammate helps you to survive far better than having a slightly bigger gun. 99% of the time I notice others before they notice me, so I like to give 'em a quick scare through direct chat, let them know that, if they make a wrong move, they're dead. This usually works, and I then let them know that I'm willing to cooperate if they are, etc.
