Okay, first, you don't 'get' a girl to like you, that implies force and it's just a little pet peeve of mine, sorry:/ anyways, smile a lot, try to be optimistic, but sympathize if you're ever in the position to, do small things for her, like offer to sharpen her pencil or something like that while you're up;) tease her a little, talk to her about her, and try not to seem to shy while speaking to her.
It depends. Sometimes you just gotta flirt and hint that you like them. Then get closer to her, alone. She'll pay more attention if nobody else is around. Then just make a move, she will definitely be to shy too. Don't worry about any "what ifs" just go for it.
First you have to start out as being her friend, then have conversations with her.. whenever you see her say hey to her ask her how is she doing. just have to talk to her that is the best thing to do communication.