If you see her in the hall go up to her and say : " stop... ( scratch chin for a sec) dont i know you from somewhere" with a smirk on your face. she'l more than likely giggle and tell u ur an idiot and that she sits like 3 seats away from you... but there you have it, you've broken the ice. From there just make general chat... make it short and sweet. if u start blabbing about nothing you'l look like an idiot,, id qualify her quick sayin somethin like... Hey, id say u should come check out this party on this weekend,,, but u look like the kinda girl that would crack a book b4 you crack'd a beer; but if you change your mind jus come let me know. Then exit.... Always exit on a high note, keep them wanting more.
Peace