Stolen from Cyn:

keep her warm if she's cold, tell her you think she's cool, talk to her every chance you get, hold her hand, tell her she looks pretty, let her pay for stuff if she wants to, sit in the park and talk to her, let her fall asleep in your arms, call her, call her back if she calls you, get her mad then kiss her, give her piggy back rides, give her space if she needs it, push her on the swings, stay up with her when she's sick, teach her something, buy her ice cream, look into her eyes, kiss her in the rain, and most important: when you fall in love with her, tell her.