I'm interested in this girl at work, and I'm trying to think of a first line to start things off (I haven't talked to her before). I was thinking of something like "Hey, were you at [some concert, place, etc.] yesterday? I was there, and I thought I saw you." Then, I thought this might sound a little creepy. Any advice?

EDIT: I'm a sophomore in high school, and she's about the same age. The place I work doesn't let the employees talk with each other (it's a tutoring center), so I wouldn't really be able to bring up something about work while working.