If you're at a community event and your set is just before the local dance school's, end your set on time (even if the performer before you didn't). You don't want to tick off every parent and grand-parent that has come out to see their kids. Also, if I didn't state it before be very specific about when you're to be paid. If there's going to be a delay, I like to know about it before the event, not during.
   Good advice from Larry Rand to us years ago was: play for good causes for free. Otherwise, get a good buck, otherwise your performance will not be valued. A lot of people organizing these sorts of events are nice and well meaning people. They may not be aware that as a performer you have some different priorities. We played at Sci-fi event a few years back. I was expecting a check right at the night of our performance. I was told that we'd get paid the next morning if the organizer got up in time, or she'd mail us the check. I finally sent a letter a month later, which ultimately resulted in a check. I could have used the money after the performance (I never have liked surprises).