Hey Fishie!
Here's my best advice. I hope it helps ease your fears a little. BE YOURSELF during Rush and try to learn a little about the different sororities (their websites are great for research purposes) before Rush so that the girls know that you're truly interested in going Greek. (It's always flattering when someone takes the time to find out about you and your sorority before they meet you.) Feel free to ask any specific questions. I'll do my best to answer them!
Good luck with Rush!! Also, check out more detailed advice in the other LSU Rush columns. A lot of Greeks (including me) have offered some insight on Southern Rush, so scan through old threads to find more info too.