Help w/ info about the PSAT?

Hey, I'm a high school sopre and was one of a small group of sophs who got picked to take the PSAT this October. How worried should I be?? If it helps any, I have a 6.0 weighted GPA and am currently at the top of my cl. No joke, though, until today, I didn't even know exactly what the PSAT consisted of. So far, what I'm hearing is pretty intimidating. Any comments/tips/advice/info?? Thanks=)