Sean,
Welcome!
One of the best learning experiences that you will encounter will be discussions with veteran officials before games, at halftime, between, and after games. This is a great time to learn and ask questions as typically we all just sit around and discuss unusual plays from the game we're working or from the previous night. These real life scenarios are invaluable in learning the rules, mechanics, and the philosophy of the game, at each level. And, don't be afraid to ask questions. As a rookie, some of the "what if's" you ask may stump even the most seasoned vet and force them back to the rule book.
Best of luck to you. Like you as a rookie, I can't wait to take the field. It never gets old!