I love this shot I got today of the singer for The Diodes, a Toronto punk band that had minor success in the late seventies. The trick is to be patient. Keep your camera trained on the lead singer and wait for those crescendos. Then PRESS!! It takes practice for sure to get photos that aren't blurred or ones where you've missed the timing.
Take a lot of photos when shooting concerts. You're going to throw away most, but it'll help you learn what works and what doesn't.