Psh... that's all in your head. First of all, don't beat around the bush. Talk to them first of course but don't drag it out forever. Confidence is a must here. Just get a feel for what they like, their interests, their personality. Find something you have in common (if anything) and ask them to accompany you to a place that has to do with her interest and personality. If she seems like the fun and games type, try go-karts or arcade, something like that. Remember not all girls are the dinner and a movie type. Try to be more than ordinary. Let your personality show don't try to seem like you're hiding something or you're a fake.

Also PLEASE, PLEASE remember that some girls are just plain old beeatches. If you like this girl but she won't even give you the time of day.... Think to yourself: "Do I really see myself in a relationship with this person?"... of course not. Don't let girls like that hurt your self-esteem. Just move on.