O.O wow. Sorarules13, you've got quite a bit of advice on this whole topic...but that's a good thing!
About the phone # thing, here's how a lot of girls feel when you ask them for their # for help w/ homework stuff:
they think that you like them, because you could just call one of your friends for homework help, instead of her.
Not every girl is like that, but it's really common. I'm glad you're starting to talk to her, though. That's good! Just make sure you be yourself, & don't use cheesy pick-up lines! Omgsh, i hate when guys use those on me. Cheesy pick-up lines can be the most annoying thing in the world, so stay away from those, & you'll be good.
If she has Facebook or Myspace, talk to her on there. Those sites are great ways to keep in touch w/ ppl.
It sounds like things are going good for you, so keep it up! Just don't try too hard - girls catch on to that (most of the time) & it gets on their nerves (that's if you get annoying). But i think you'll be okay!
Another thing, just remind yourself that you are so lucky to have found someone that you like this much. I'm 15, 7 i don't like any of the guys that i know. I go to a private school, so i don't see as many ppl as other ppl do. I don't know a lot of guys, & the guys that i do know tend to be immature & act like they are the coolest guys in exsistance. It gets annoying, all too quickly. I'm 15, & the only guys i know that aren't immature are seniors, & we're too much like family (no, i am not related to any of these guys, just in case anyone was wondering) to go out.
But, i really don't care about having a bf right now, & i've never had one (yes, i am okay & no, i'm not crazy.). All i'm trying to say is - remember how lucky you are to even have a girl that you like this much. It sounds like you really like her, for who she is.
One last thing. Don't worry about messing up when you're talking to her. Like if you try to say something, and you accidentaly say something else. It's embarrassing when you do get tongue-tied or forget what you were going to say, but don't worry about it. Nobody's perfect. A lot of girls think it's cute when guys mess up like that. It kinda helps the girl be a little less shy, cause it shows that you're a human too, and it's ok to talk to you normally instead of being shy. (ALL humans mess up in convos - if you haven't yet, you will. Just wait...)