Girls will be more forgiving of your lack of talking if you are attractive, and many girls like to do the talking, anyway, so the thing you need to do is to just get them talking. At 17, you have a lot of common ground with girls your age that you can discuss: school, college plans, music, how you spend your school breaks, jobs, hobbies, etc. Really, just try talking to them like you would anyone else. You might want to try to practice on girls you find less intimidating for a while... I don't suggest you approach the most popular girl in school initially, because ALL the boys are doing that, and it may shake your confidence.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?