Go into your movie and walk up and sit next to any HB's you see. If that seems a bit to forward you can even slip in "Is this seat taken?" to which the answers should sum up that girl for you.
"No, but there are more seats up there" - Not interested
"No" - She'll give you a trial run
"Yes" - Forget Her
"Yeah my friend's there, but you can sit on my lap" - *ding ding*
Once your sitting down just start up some casual chat about the movie, how good that scene was... whatever. If you get things going you can start to kino, and lean on her. Use your inner DJ