1. Make the first attempt to get you "in the meet" If you have competition and if it is within your capabilities try and move up a place or two on your second attempt and again if it is within your capabilities go for the win on your third. Now if you are lifting unopposed or your closest competitor is 300 pounds ahead of you then your focus should be on going for something close to your max but fairly sure of on your second attempt and go for a new PR on your third.
2. be fairly certain of your openers but if warm ups suck do not be afraid to lower them. Nobody remembers what you open a meet with unless that is what you bomb out with. Seconds or thirds look at your competition or set some goals but again don't be afraid to change them before turning them in.
3. Warm ups can be tricky. But if you happen to be in the second or later flights then start warming up just as the flight ahead of you is about to start their first attempts. Being a beginner it if far better to warm up too early then too late. As you gain more experience you should finish your last warm up about 10 to 15 minutes before your first attempt. But the most important thing to remember is you are not there to get in a work out, get warm but don't push yourself in the warm up room, that is what the meet is for. Personally after the first couple of sets the rest of my warm ups are singles just to get used to the weight.
Try to pay attention to when your flight is going to be up. At most meets you can usually find someone willing to give friendly advice. Relax and have fun.