Probably the best thing you can do, Vince, is just ask. Simply be stright forward. If she says she has a boyfriend, she might just be shy to say yes. If she DOES have one, then just wait, it might not work out.
There are a few other things you could do, but I'd not do them if I were you. It might end with her thinking you're weird or something. And then you might not even be able to be friends. (Kind of like what happened to me)