If I were you, I would check out both the National webpages for the sororities on your campus -- then look at the links to different campuses. You will see that there are no cookie-cutter stereotypes for any of the NPC sororities.
A good place to start:
http://www.npcwomen.org/
Someone once told me that sororities are like individual people. You don't assume that all the people with the same name are the same, therefore you can't create a stereotype of every person with that name. People are different everywhere, sororities are different everywhere.