[33girl]

Sit in the caf, near the sororities, so they can see you. Be sure you look hot.

When you DO have mixers, make sure you publicly thank the sorority you mixed with, thru the school paper or Facebook or whatever. Not only is this the polite thing to do it lets other sororities see that you're mixing.

Participate in intramurals if your school has them.

If the guys have time, get some of them to step outside their comfort zone and join extracurricular activities that aren't specifically to do with their major.