If You're in the Band

How to Deal with a Sound Bozo
If you run into a bonafide turf-conscious sound moron, you can waste a lot of psychic energy battling them. Don't get yourself worked up. One approach is to humor them, and try to manipulate them into doing it right. If this doesn't work, let them waste the first dance or two. Then, after they've forgotten about it (or left the room), be ready to do a quick re-set of your own. You need to be a hawkeye, because they'll sometimes be missing an entire instrument in the mix.

If you do a lot of gigs, carrying your own sound may be worth it for this alone.

Working with a Good Sound Person
It takes a minute after the band starts playing for even the best soundperson to get it together, so don't hover over them - offer comments once it's basically under control. The best arrangement is for someone in the band who knows about your particular sound issues to come out and listen on the second set.

Also, don't slide in late if you've got a complicated setup or surprises for the sound person. They've got enough to do!

When You Have to Mix Your Own Band
Stay out and use the first set of tunes to listen, even if there's been a sound check, since the sound changes once the event gets going. And adding your instrument the next time is more exciting than dropping it to re-do the sound.