Hi glentiaw, i'm interested in photography myself...still learning so hope i can help you out.
Anyway, assuming that you aren't using flash and have a digital slr camera:
basic rule of thumb would be ISO at around 800 or higher (will be able to see a lot of noise but lan lan, and shouldn't be a prob unless you're looking to blow up and print or somethin). If you're using film, think you can afford to get slightly lower ISO, but maybe someone with more experience with film cameras could help with this?
In terms of aperture, you probably want it to be around f 2.8 and not higher than 4, cuz you probably wanna capture individual members of the band, so depth of field shouldn't need to be too deep. May have problems if you wanna catch more than 2 members at one time though, depending on size of stage and proximity of members.
Think shutter speed wise depends on your camera model and what it can take... But if you've a digital slr would be good if you play around with it before the gig to see how much motion blur you get in the particular lighting. Generally, unless you use flash you're going to get motion blur regardless, cuz you won't have a shutter speed fast enough to freeze the subject
Try to get as close to the stage as possible, if you're friendly enough the security may even let you in for a minute or two to snap some photos. If you stand to far back and try to zoom in with your 75-300mm, chances are you'll get a lot of camera shake.
Try to time your shots with the movement of the lighting effects so you can get natural backlight or sidelighting. I personally don't like catching the light source directly in the shot itself though cuz I think it really diverts attention from the subject and all....
Anyway, this stuff is pretty basic to all the pro photographers out there and I'm still learning. Anybody else care to help out?