Nowadays dark is no more a problem as it once used to be. These gigs are often dark but with modern cameras it’s easy to produce good results at the high ISO. But you should remember to shoot RAW. Shooting in JPEG mode will not give you the latitude to correct colour levels and noise. Always use the manual mode on your camera. It is difficult to get anything good about ISO1600 if you are shooting with film cameras. But you can get good results while taking a good shot only if you know when the light is good to shoot.
If it is your first gig you will be tempted to shoot every single second of the performance. Well it can be done but you’ll soon find out that a high percentage of what you have shot is dark, out of focus and not usable and you have wasted a lot of time going through all your images. Patience is what you will need to wait for the best moment to shoot. Follow the lead singer check the angle where his microphone is not in his face and see where the lights are or maybe blows a kiss in the air just keep shooting. Follow spots are often seen in big shows and are usually good quality and they stay consistent throughout the show. These are often operated by a person and all they have to do is follow the artist on the stage.
Try to capture the expressions of your artist. Not all shows are lit up and some shows can be really challenging. Check how high the ISO have your camera can go before the images get very noisy. Remember to not mix flash and smoke or you will only have fuzzy images. Just be at the right place at the right time and everything else will follow.