You ALWAYS put your best foot forward. Big smile, friendly attitude, laugh a lot, etc. This does two things: one, it put the other folks a bit more at ease--once they realize you're not after their stuff, they'll be less prone to knee-jerk hostility. Two--if the situation takes a horribly wrong turn and it turns out that you do need to turn into a right bastard on the spot, you may well catch your opponents off guard.

Note that being friendly does not necesarily include immediately offering to share all your stuff (or even acknowledging you have stuff to share) or shelter. Nor does it mean you let down your guard--if someone's intent on looting, they're going to go to it regardless of what demeanor you present. But, assuming that most peole you encounter will not have mayhem on their mind, this should work. Just IME and all that.