As I said to my roommate who was a sophomore at the time when we were going through recruitment (I was Freshman)...
Be the best person you can be... Be yourself, show those sororities who you are and forget the rest
As long as you're a good person and have a good time, then you're ok in my book...
A 3.0 is ok, and it is acceptable to Panhellenic standards, but by now you can't do anything about it, so relax... don't think of it as a competition (although it is)... but if you go into it as a competition, you're not focused on the real reason why you're there: to find your potential new sisters.
Be real and relax, and you'll do fine
Best of luck to you!
-OSSK