Don't tell her you like her. Ask her to a movie or something, then go from there. Never actually say "I like you." Send her signals. She'll figure it out. It's alot more fun for them that way than a guy just coming out and saying it. It builds up anticipation and it causes her to wonder "Does he like me or not?"

Play a few games with her, and take things from there. While you're doing that, become better friends with her, but also don't forget to flirt with her.