Chat up lines are a total no no. Don't see her as a potential romantic interest, just as a potential friend. Ask her questions about what she does, whether she works full-time or is at school or uni. Tell her about what you do. Talk to her about your friends, family, holidays, what you like to do in your spare time, or anything you like, really. If you're not sure what to say, just keep asking her questions and take your lead from her.
You should also keep an eye on your body language. Don't hunch as though you are scared of rejection. Don't be afraid to look her in the eye, but at the same time, don't do it for long periods of time, because staring can unnerve people. The best thing is to look her in the eye for most of the time she's talking, and when you're talking, look at her, look round the room, gesticulate, just basically be enthusiastic and animated about what you're saying. Be lighthearted, rather than too intense.
Definitely be yourself. Don't pretend to be someone you're not, but recognise that you are interesting and worth talking to as you are. If she doesn't like the person you are, there's no point trying to impress her.