Anyone who I really like eg Starsailor and other little indie bands. I sign up to their mailing list or message boards and it gives out the info there. I have met bands at signings, before or after gigs. I even got backstage during an Audioslave concert but that was cos one of the promoters spotted me standing uncomfortably pregnant at the gig. So I got to meet Chris Cornell. If you show your face at siignings and stuff enough you'll get invited to the aftershow parties.
theres a convention thing in London soon with signings etc, was in the sun yesterday, cant remember where or when, but lots of famous people will be there to have your pics taken with.