You've had some good advice so far, I shoot a lot of concert photography. I mostly shoot the larger well known groups.
Like all photography, if you really want to do things properly you cannot rely on any auto modes, you need to meter and set everything manually and don't forget that many stage shows are going to constantly have changing lighting so keep manually metering and resetting.
You'll also need to master techniques in balancing lighting, and a lot will depend on the individual venue when you get there you'll have to quickly analyse it and set it as neccesary.
And as others have said, the 3 song rule is very normal, and its not as much time as you might think, not to get the shots you REALLY need, so you need to make every shot count. Don't waste time looking at your display. Get it right and shoot.
Quality lenses are an absolute must.
Paul.
www.photographybyriddell.co.uk