I actually take some time before shows now to mentally prepare for something bad to happen. I know that sounds awful but it can EASILY ruin my night otherwise. I take time to realize patrons, promoters, cops, and other groups may be unnecessarily mean to you for no reason. I've been to so many shows with hijinks that at this stage it's almost expected.
If possible, try to take down names/descriptions as the folks running events (and owners) are *really* conscious of personnel and bartenders chasing away customers. Still, just get out of the situation. Nothing good has ever come from alcohol soaked, short tempered, making-up-for-something jerks. It's not just standard douchebags either: I've had both promoters and police talk to me out of absolutely nowhere like I was 8 kinds of stupid.
- Police: keep it calm, keep it polite, use "Sir". At least where I live I do this "super sober" technique where I'm short, clear, direct, and straightforward. Other places you'll want to always smile and pretend you don't fully understand (the warm foreigner tactic).
- Drunk Frat Kids: You may easily get pushed or otherwise accosted by someone trying to assert their manhood. Some of these guys are actively looking for fights so you just have to look tired, drunk, or sick to avoid interactions. You might point this out to someone who works at the club "hey that guy in the red shirt is going to get into a fight before the night is over" but I'd leave it at that and try to stay outside of his area.
- Security/Bouncers: I've met a few of these. Realize that they deal with the above group (Drunk Frat Kids) and are basically being asked to manage a huge group with no real authority. They are 90% attitude because -- in this world -- they are all afraid of a lawsuit. I am always assuring them I'm not someone they need to worry about and leaving the situation as calmly and quietly as possible. Yes sure absolutely sorry are pretty much the only words they can discern. Your very reasonable, obvious questions probably aren't welcome here.
Next: Part 4: Encouraging Good Vibes