What should I do ...??/?

I need to figure out what to do about the girl I like. She's not your average girly girl and is more of a mature, well mannered, shy, but still is a fun and out going person. We dont talk a whole lot at school and usually she starts the conversation when we do. BUT most of our talking is over texting for example in one day we racked up about 150 messages and we talk almost everyday. I know she doesnt just reply to my messages absent minded because usually the next day she brings up our conversation at school ,and she sometimes starts the conversation I need to know how to go on about this cause i wanna go out with her