Congratulations! HS ball is faster and more skilled, which in some ways makes it easier to officiate because violations or fouls stand out more. Remember, your "jitters" can be used as a positive to remind you to do your best, stay in the game,etc. Focus on your area. Call your game. Know you have a partner or partners out there on the floor who will be helping every trip up and down the court. And remember, even the most seasoned official was a newbie once. Have fun and enjoy the excitement! Oh yeah, one more thing: Ignore the howler monkeys who are afflicted with stupidity and large vocal capacities.
PS: tjones1 would tell you to make your your pants are zipped!