Go off campus: Far off campus. This is where your school keeps the ugly girls. Girls that shouldn't be allowed out while the sun is up, girls that haven't known the touch of a man since their fathers used to beat them for being too unappealing, girls that you can get with.
Find the pretty one: Here's the thing, there's always one decent one, surrounded by the shroud of rancid, grease faced, beer gutted, lower back tattooed, pit stained ex-field hockey players. You just need a keen set of eyes, because the pretty one my friend, is all yours.
Build her self esteem: You've been here for ten minutes and you want to kill yourself, this girl has been living here since school started. She's spent all her days with a bunch of seniors who used to be ugly their freshman year, now there are no words to describe their heinousness. But you can save her, and the beauty is, any line will seem amazing at this point. Try, "I can see your nipples through your shirt" or just look right at her and say, "I'm imagining you naked." Pause, "Not bad."
Whisk her away: It shouldn't be hard to get her to leave her beastly friends, just hold out your hand and when she takes it, lead her up the stairs. Once at the top, she takes over, slamming you against the wall and throwing her lips against yours, her shirt flies off and your hand shoots down the front of her jeans, the button is stuck but whatever, you spin into her room and shut the door, the jeans are torn down and yours follow" You get how the rest works.
Leave quietly: You can't risk seeing the beasts that live in the other rooms in the daylight, you can not return, but you left your number on her desk, she's welcome to come to YOUR place.