For concerts I always shoot raw with noise reduction switched off at relatively high iso, as post production software can make a better job of noise reduction.
I also tend to under expose shots to get a faster shutter, and avoid blowing out face highlights in situations where the people on stage are well lit but surrounded by dark. If the stage is lit with primary colour lights you'll often blow out a single RGB channel. Again, it's easier to increase exposure in post than it is to retrieve blown highlights.
You can get some great directionally lit black and white conversions by using a single channel if the lightings like this, always worth quickly soloing channels in photoshop if you have it.
With regards to Leslie75 saying 'as many pixel as you can get' well depends on your choice of equipment but low light photography is generally best done with the largest sensor you can get, and lowest pixel density. Anybody who's ever used a nikon d3 or d4 (the best low light cameras available) knows that less pixels wins in the dark.
I often shoot manual if using a fast lens and time shots for performers to move into my preset narrow focal field (e.g in between songs will focus on the lead mic stand, tweak back a bit then fire of shots as the singer approaches the mic. This means I can get well timed shots rather than waiting for a focus lock which may be delayed if the the camera struggles to get a fix and 'hunts' in low light.