Some of the above notes like always making the time to talk to her (just don't go majorly out of your way... stalking is to be avoided because it will freak the poor girl out!!!), but there are also nice little things you can throw in like always making sure you open the door for her and her friends, picking up her bag for her when she's too tired to reach, letting your hand linger on hers a millisecond longer...!
Be a gentleman, be assertive, show her you're comfortable within your own skin and she'll be drawn to it
It's all about the subtleties. Us girls love those and will pick it up like *that*.
EDIT: Listen to Dr_Doom. Let the girl talk. The more you listen, the more brownie points you clock up.