Just be confident and practice at home are the best tips you can get. If you know what to expect and you are ready for it, you will do good! And don't forget to thank your gorgeous pony afterward :) Good luck!
The most important thing about taking a green horse to their first show (assuming it's her first too?) is making it a good experience for them. Lots of praise, take things slow, keep her calm and happy. You're not there to win or for the ribbon, you're there so she can go in the ring and find out it's a fun thing to do. Make sure you prepare prepare prepare at home! Do a class that's easy for her. When she gets some experience under her belt, go back in the ring and do it to win it! :)
If you have different equipment or clothing for the show than what you use or wear every day, wear it for a couple of practice sessions before you go to the show so both you and your horse get comfortable with it.
Other than that, I always try to relax and enjoy the experience. Don't expect to win ribbons, but just try to have the best ride you and your pony are capable of. If that wins you a ribbon, fantastic. If it doesn't, continue to work and try to improve in your next show.