Just a couple of things off the top of my head.
-Get someone that you trust to come along to handle you. Even though you are lifting raw and don't need help with gear it is nice to have someone else help you with your warm-ups so you don't have to load, put in your attempts, and handoff on the bench. They are also there to talk with you and help keep you focused. This is probably the most important thing you should take care of.
-Pack plenty of food and Gatorade is you are doing a big multiply meet it could take a LONG time. I have been in a few that started at 11AM and ended at 7PM.
-Have a plan for your first and second attempts, then take your third based on how the second attempt feels. Remember this is your first meet so you are going to set 4 PRs (bench, squat, dead, total) no matter what!
-Hit your openers 1.5 to 2 weeks out then just deload and stay loose. You won't get any stronger that close to the meet, but you could get weaker by not resting properly.
-Open light! This is your first meet so there will be nerves and other factors at play (monolift?) I would make sure your squat opener is something you could hit for an EASY triple in the gym. There is nothing worse for your momentum than to miss your opener. Often after I crush my opener I relax and the rest of the day falls in place.
That is all I can think of off the top of my head. Just remember to have fun more than anything else. You are young and will have loads of meets ahead of you if you decide to stay with the sport.
Good luck and I hope this helps a bit!