you can't just ask a girl on a date. you have to built at least some sort of relationship first. I would do this by just mellow chatting, until you get to the point where you two can talk about the nitty gritty stuff in life, and really understand each other. at this point, you will be able to gain emotional closeness with her, and she will begin to want you as much as you want her. then, when she wants you to ask her out, you ask if she would like to go on a date some time. mind that to get to this point, you've already had to hang out with her quite a bit, so don't think that "lets hang out sometime" shit will work.