Smile at her in the hallway. Girls love that! Talk to her more often and use the word "love" sometimes. Like: Yeah, I LOVE baseball!" If she likes you, she will catch on and flirt with you. Also, what my friend does is he talks to his friends about it, and eventually it will get around to the girl!! But that is a bit risky. If you really like her, go for it and tell her! Girls are too shy to make the first move, so be the guy! Good luck!