Female Advice? (coming from a teenage boy)?

So there are three girls I'm interested in, and here's the lowdown: At the top of my list is a girl who is in most of my classes, and she's really nice. Only she doesn't talk to me the way she talks to her friends. Next on my list meets my appearance preferences: Brown hair, glasses, moderately thin, and Russian. We're really friendly with each other, but we almost never see each other. Last on my list is in nearly the same situation as the first girl, except I see her less and she's more open to me.

Who should I go after? How should I go about it? Thanks!