How to get started?

[prosec34]

I'd suggest you get the NFHS case book in addition to the rule book. Going through the case book will give you a great introduction to what's going on with NFHS rules.

Mechanics are the big thing you'll need to master quickly. Thus I'd go see as many high school games as I could before the season ends. Just sit and watch what the officials do, especially the wing guys (linesman and line judge). Take notes on what you see them do. In fact, I'd suggest you ask the assignor if he could put you in contact with the referee who will work a particular game so that you can attend their pregame meeting. That way, you can hang around them after the game and ask questions as to why they're doing certain things. You'll make a great first impression acting so interested in such details.

And when you finally get a chance to be on the field, hustle. Act like you're always being watched by someone you want to impress, because you never know when you are.