Using a NikonD5100 at a concert?

My friends are putting on a concert at a smaller venue/bar tonight and have asked me to use my Nikon D5100 to snap some shots of them. I'm allowed up on stage with them etc.etc. I can shoot anything from anywhere. But I've never taken the camera to a concert and I was wondering if anyone had any ideas as to what the ideal manual settings would be? Venue will be dark with some colorful lighting on the band.

Best would be to use a flash, but without flash, you will need to use the largest aperture your lens has, and then attempt to get at least 1/60th of a second shutter speed. Set ISO accordingly.

the thing about manual setting is that you can't foresee what you will need to use.

I don't know about working in full-manual mode for a gig, you won't normally have the time to set things ups shot by shot. Now I'm not familiar enough with the D5100 to know if this will work, but here's how I'd go for it. Set the Auto ISO range if you can, so that the maximum is as high as you are willing to accept. Then shoot in the shutter speed program mode aiming for 1/120th sec or better using a lens with a sensible focal length and a large aperture. If you have an external flash then take it and if possible set it to bounce off the ceiling of the venue, if it has any "creative" modes agree on their use with the group before hand - oh and it may look bonkers but get any levels that you can set up before the group get on stage. Try to work with the venue lighting. Agree on some sort of signal with the group so they can let you know if you are p*ssing them off (it happens), and try not to get in the way such that it annoys the crowd too.
If you can build up some rapport with the venue staff too it may well help for future events.

You have to experiment. If the light level on the stage is not changing very much or very fast, manual exposure can be best, because it is not constantly changing your setting by every little movement that alters how much foreground or background is being metered. You want to capture the most photogenic moments, but taking practice shots on the not so great scenes will be helpful in getting your settings right by the time the better photo ops arrive.