Take your time and don't worry too much about it. If you do see her around a lot, chances are she's into going to much the same places as you do and possibly likes much of the same things as you do, too.
All I can recommend is not using some cheesy pick-up line or something to get her attention. If you see her again in a place you both go to, call her out. Tell her you've seen her around. Ask her if she saw anything good at the record store, then bring up some of the music you listen to if she doesn't appear to be in a hurry. Mention spotting her at the concert. Tell her you tried to track her down because she was somebody you'd seen around before and wanted to hang out with, but you lost her in the crowd. Just let her know that you both wind up in the same areas, and therefore you probably have a bit in common. Don't try to hit on her first off, just try to get her attention and see if she interests you. If you like what she's talking about, continue the conversation. Don't go into a verbal exchange with her with "you've got big boobs and I want a date" in your head. Just try to be friendly. Treat her like one of the guys.
If that doesn't work, oh well. You'll still see her around and she may find you interesting enough to aproach you herself at some later day.