Well to let someone you know that you care for her is BE THERE for her sometimes girls need people to be there for them. the way to do this is to get her to notice you.
BUT WARNING: don't be a jerk or a show off about it. do little things for her but don't be pushy. carry her books or stuff for her once in a while then take her out to eat. DON'T push her into things she doesn't want to do. BE a gentleman. seriously just be a good friend to her and its sure to work
I would also suggest that telling her your love her would be a good thing to do.