I want this to be perfect, how do I tell a guy I like him?

Don't do it over Facebook; it won't have the same vibe as doing it in person, and it won't feel as personal. Just ask to talk to him alone, and walk away from your friends for a few minutes. Just tell him that you've grown to fancy him quite a bit, and that you've been getting that vibe from him and would like be more than friends.