It's really hard to stress this enough, HYDRATE, HYDRATE, hydrate. St. George is high desert so the temp doesn't get as hot as Tucson but you will dry out. Start the night before. I prefer a 50/50 mix of water and Gatorade so not too much sugar. If you can relax and have fun with your buddies you will have a great time and probably finish higher than you expect. As Mark said shoot YOUR plan at your pace. (Guilty of thinking I was as good as the Master class shooter before me and tried his plan. Didn't work out so good.) Pay attention to the walkthrough, it helps, ask questions.
Stuff happens, weather changes, the gun pukes, you get the morning or afternoon sun directly in your eyes, that gas station sushi was not such a great idea,...etc. Remember you went to have fun so laugh a lot and enjoy the ride.
Have dinner at Cappelettis Restaurant, best Italian place I've ever eaten.