I photograph musicians in performance. Maybe some of my approaches might be transferable to your situation, maybe not.
*) When shooting or moving around off or on stage black clothing keeps one less of a distraction.
*) I never use a flash. I feel it is disrespectful towards both the musicians and the audience. As a musician I feel it is very distracting, as a member of the audience I feel it is very distracting when other use flash. If I need to use flash then it needs to be a closed auditorium and shoot set up specifically for that purpose.
*) I use slow speed film, (100 asa). If shooting digital and the end usage is small enough, I'll use a higher speed / lower resolution setting.
*) I try to know where the spots (lights) are going to be and only shoot when the subject is in those spots, giving me enough light to shoot the slow speed film with a shutter speed that will stop the action. Shoot when the subject is there and take what the situation will give you. Most of the time when a musician is doing a lead and the expression are most expressive they tend to be highlighted with spots anyway so in my case in works out okay. Blurred motion is acceptable a lot of time, maybe even more in your situation.
*) Study the art of the performance. For instance, as a musician I generally have a feel for when breaks in songs are going to be, leads are going to happen, etc. One can be prepared for the moments when specific light, lack of movement, climax in expression, etc, etc., all happen. Something like, "chance favors the prepared".
*) Generally long lenses are used, 200+ (35mm)
*) I work individuals rather than for group shots. The light is almost always too contrasty, (some musicians in spot lights, some not, some stage areas totally black, etc.), for successful overall stage images. Some larger productions may have overall lighting that might work, but most of the time not.
*) I watch a lot thru the viewfinder. Sometimes I spend so much time behind it people think I'm doing video.
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