I always felt that it helped to have a sort of script memorized, so that when conversation wasn't flowing and the PNMs didn't have any questions, you could "create" the conversation by yourself...and they could just listen. Sometimes, you'll say something that gets them going. If not, at least they walk away with a ton of Phi Mu info...
Think about answers to these questions...the advantage to these is that a lot of them can (and should) have a personal take, so each sister will answer questions differently and not bore the PNMs to death!
-Why did you join Phi Mu?
-How was your new member period, and how did you adjust to sorority life in general once you pledged?
-What sort of leadership opportunities are there in Phi Mu?
-What campus activities does Phi Mu have a presence at ? If you're in one of them, talk away.
-What has your specific chapter done to work for Phi Mu's philanthropy?
-How has Phi Mu affected your life (in a *positive* way, mind you!!

)
-What kind of contact have you had with other Phi Mus not in your chapter, and how did that help you? (Again, good things...)