I've got a crush too, and I can't tell him. I know exactly how you feel! When you two get alone (if you get alone, unlike me) just sit down and hold her hand, play with her fingers, (I love it when he does that to me!) and look her in the eyes and tell her you have a crush on her, and you want her to be your girlfriend. Hope that helps! I'd love it if he'd say that to me ;)
Tell her right before you have to go to another class WITHOUT her in the next class so that she has time to think, and if you're that uncomfortable saying it face to face, like I am, give her a note at the end of class.
Girls like boys who are bold so just go up to her and do it. Try to do it when she is alone. If your lucky she will have a crush on you. I did this with the guy i was crushing on an it worked s it will probably work for you.
just walk up and lay one on her give her a passionate kiss that takes her breath away and walk off give her time to take it all in and even if she doesn't reciprocate who cares you kissed your crush and proved to your classmates you've got balls
well more details would be helpful. but...you should abandon fear.