Remember that the greek community is very small. If you make unflattering comments about XYZ to ABC, you will make yourself look bad to both chapters.
Also try to represent the best of WHO YOU ARE. Don't make things up, or pretend to be something you aren't. If you aren't the most athletic, don't play along and act like you are. Show your strengths, but don't be afraid to laugh at yourself a little either. When intermurals came up in conversation, I remember telling one girl that I ran like a duck. (It's true!) but that I loved playing volleyball. This made us both laugh. (She was later my big sister!)
Remember that the girls in the chapters are a little nervous too. They want to make sure that they are making a good impression as much as you are wanting to make a good one.
If it's off color, don't say it. If you wouldn't repeat it in church... don't say it. I'm not saying that you have to act prudish, but rush isn't the time to tell "band camp" stories.
It IS a competition, and you ARE being judged. But guess what, you are judging them too. IMPRESSIONS matter. If you don't bathe or brush your hair... it MATTERS. You don't have to be physically perfect. (Who is?) but do the best you can with what you have. Show a graceful poise.
AND BY ALL MEANS USE MOUTHWASH. (Sorry, rushed a girl with FOUL breath once....
)