Wow.. 6 years, huh? Have you two even talked? And does she have a boyfriend already?... Anyway, telling her in person how you feel is hard. No one should think its easy. Ask her out in a cute way. Make them all add up to each other. Okay so first have a friend go up to her and say, " I know someone who likes you.. But I can't tell. You will have to figure it out" Next write a letter and tell her how u feel, and slip it in her locker. But don't say who it is, sign your initials or write - from your secret admirer. After that write a letter and tell her to meet you somewhere after school, but this time sign your name and AKA your secret admirer (so it isn't creepy) And now meet her with some roses and tell her how u feel in person.
Or instead of all of that just walk up to her with your phone number on a piece of paper and write bellow it: 'call me maybe?' And then ask her out over the phone