well, my own opinion:
1) Start small, photograph local bands in small clubs
2) Give copies of the prints to the musicians
3) don't pop flashes in their faces.
4) I use 400 or faster film, no flash and fast lenses - no need for a flash
5) shoot enough, carry samples with you - you'll soon get invited to tag along
6) don't drink when working -- you're likely to lose gear or become a complete knob...
7) build relationships with musicians and club managers, big names play small clubs often.
8) don't be an arrogant tool when dealing with the musicians.... They're the star, not you.
9) blend in - I recently shaved my head, I wear quirky rock and roll clothes - I look like something they are used to seeing
10) sometimes you have to be cunning, creative, and anti-authoritarian- -- rarely, you'll have to sneak your gear in...
11) be persistant