You can find answers to this all over. The thread called "so what have the guys been saying before/after gigs?" might help. Other than that just browse around!
Usually, if they're able to come out after a show then it's fairly easy to meet at least one of them. Find out where the bus is because it'll either be by there or by whatever door they use to go in and out of the venue (at least in my experience). If you get there early and join the line to get in, you might be able to find out this information ahead of time by just observing.
Also look for the other 50 people waiting around, haha. Good luck!