Start with the highest ISO your camera can manage without too much noise ("too much" being entirely up to you, of course). Use as wide an aperture as you can and still keep what you want in focus. Then adjust your shutter speed until you get what you want. Expect to spend a fair amount of the first song just getting to where you can shoot something usable. Practice adjusting your shutter speed quickly because many concerts have shifting lights, sometimes fog, and band members have an annoying habit of moving out of the light.
When you start getting something you like, do what you can to minimize shake. Lean against a wall, brace your arms on a table. If you're standing, pull your elbows close to your body. Anything that will help you keep your camera steady is good.
Watch the performers and try to get a feel for how they move. You can almost always find videos of a given band online so watch a few beforehand to see how they perform certain songs. If you can tell that the lead singer always pops his head back at the chorus, focus on his mic, frame your shot and wait for it. Does the lead guitarist pull her axe vertical to hold that note? Be ready for her. Be prepared to shoot a few dozen shots of the drummer to get one that works. Drummers are the fastest moving and worst-lit people on the stage and they're the hardest to shoot.
Try shooting singers in between lyrics, that's when you'll get smiles and sneers and quiet moments and laughing and tongues sticking out. Mix up what you shoot: get the whole band, get each member individually, try to get shots with two or more bouncing off each other. Note that if you shoot an individual band member and don't need anyone else in focus you can increase your aperture size even more and get more light. I like trying to get at least one good shot from the side of the band interacting with the audience.
Avoid using a flash if you can. It'll be nearly impossible to light all the band members very well, plus you lose the reds and blues and purples that make concert photography fun.