me also being 15 and being the intelligent smartass that I am, i can help you out.
1.DONT call her a chick EVER EVER
2.If you can't work up the courage to ask her out, then either you're pathetic or she's not worth it.
3.When you do ask her out, take her to see a movie that you have prior knowledge will be bad but she doesn't know it. Then, when it's over, you can exclaim you're sorry and she will feel more affectionate towards you for being "innocent" (she will then, however, hate the movie forever, but who cares?)
4.Then, to "apologize" to the movie being "unexpectably bad", buy her a giant stuffed animal (unless she seems particularly like the kind of girl that HATES them, in that case get her a cheap necklace or a bracelet). If you opt for the giant stuffed animal, try and get a puppy. If you cant, any fuzzy "cute" one will work.
5.After that she will almost guaranteed like you (and you will have spent $20). From then on, try to act manly but not to the point of being a jerk or being stupid around her, and try to act innocent whenever things don't go as either of you planned. I personally have abandoned girls though because i realized that for now, being only 15, i personally think i am too young to be worried about this sort of thing right now and that they would just distract me from my academic career. GL, HF, and USE PROTECTION (JK, no sex till marriage ^^)