Answer:
Really, it's a matter of getting to know the girl and allowing things to naturally happen. Beyond that, you shouldn't be shy to talk to a girl, and maybe ask her out if you like her. Try to get to know her and make her like you... invite her to a few things such as ball games or the movies.
Sometimes it naturally happens. For me, I knew a girl for 11 years and I didn't even expect her to like, but it happened. She told me she liked me and we just ended up dating.