Ask her out. Just say, "I'd like to take you out, do you have time this week?" If she says yes then ask her what she likes to do and plan something. Girls like it when you plan to do something. So many guys are vague and wait until the last minute or they say "let's go out sometime".
When you know close to everything about her, know what she likes, what she prefers, what she doesn't like, know her better than you know yourself, thats when you truly know what you are really doing, and wheather or not your doing the right thing