Small Music Venues
Concerts are near impossible to meet someone at. Between aggressive crowds and assaulted ear drums, move making becomes difficult, to say the least. But shows at small music venues are a different situation entirely. Often bands are bringers, which means they're required to bring people to the venues to perform, so there will invariably be a group of girls who came to show their support for their friends. If you want to be creepy about it, there are usually 5-6 bands to a line-up for these types of shows, and the guests from the first band usually leave right after, so you could technically kick game to a new crowd five times over. But yeah, like we said, super creepy.
How to approach her: Seem genuinely enthusiastic about the band on stage. Ask her, "Have you seen this guys before? They're great," in which case she will tell you their her friends/co-workers/neighbors and inquire about who you came with. Conversation successfully started!