Welcome to the family, DGIRL!! Other than the general awesomeness of ProgPower like Rider of Theli and AMBR have mentioned, you can expect to wish you brought more money, better shoes, more snack foods to share with your friends at the all-night afterparties, and a liver made of steel
One hint, get there early and go straight for the table selling the event shirts. These sell out quickly, especially some of the smaller sizes, and after the weekend is over you're going to wish you had one
Also, make sure to check the schedules for performance and autograph signing times.
Don't bring a camera without anticipating the wait in the inspection lines.
Expect to want food after the show, so follow the crowd to the nearest China Buddha restaurant.
And lastly, be prepared to fall in love with at least ONE new band by the end of the weekend. It's worth it to check out a few songs of each set. You never know what you're going to find...