You don't say what lenses you have? In night clubs it can be a bit dark, so lenses like a F2.8 or F1.8 could be ideal. Most night-clubs don't allow flash so, that may be a no no. Need to check with the venue first. If you use a high ISO then you will get gritty images but you need to keep your shutter speed up to at least 1/250s unless you want a motion blur. If you have time to visit the venue before the shoot, it may give you an idea where to position yourself for the event.
If you do have problems with the light, wait until the artist is lite by a spot before taking the shot as you will get better results. Otherwise, it a case of taking shots and check the histogram for each one to see it you have to make changes to shutter speed/ ISO.
