If you want to eliminate a LOT of problems:

Treat the sound person with respect.

Realize that they make their living doing "rock", so if you don't want as much "high end" or level, tell 'em.

Explain to them the acoustic properties of your instrument, and give them brand names and models of any sound enhancement equipment you're using from the stage.

Trust me your sound will be much better than if you try "attitude" on them.

Since I usually take at least four instruments on stage with me, I warn 'em ahead of time that the silly little one (lap dulcimer) is going to require a lot more gain than the banjo, and that the Twelve string is prone to feedback. I ask is it OK with them if I do individual mike placements on my own. Obvious, really, but I think they appreciate the courtesy.

Rick