Pat,
I too am a new wrestling official, although I have been a soccer referee for 14 years. I am having a terrific time officiating wrestling and am fortunate that I found a few really excellent resources to help get me started right.
First, spend a lot of time on Matref's site:
www.wrestlingref.com
there is a wealth of information there including some advice specifically for new refs.
Also, spend time on the NFHS wrestling forum. Since you want to officiate HS wrestling you will want to focus on the HS specific rules so don't get distracted with NCAA or other forms of wrestling until you are really familiar with HS. You will have to track back to mid November to find the "Advice to the Newbie" thread that I started, but I can tell you, the advice I got there was a HUGE asset to getting me started off right.
The obvious advice is to really study, read, and reread the rule book. Because I was never a wrestler myself, I have spent a lot of time learning the rules -- more time, I'd say, than the other rookies who wrestled and think they understand the rules already. Although I am definitely stronger than the other rookies in rule knowledge, I am much weaker on knowing and recognizing holds and moves. A couple months ago I didn't know a whizzer from a suplay. Because I have watched so much wrestling over the years, I had a good basic understanding, but not enough to really know the sport. If you don't know various holds, don't be afraid to ask the veteran referees. Believe me, they don't mind putting a hold on you to teach you a thing or two! Also, you can type in key words like "Granby roll" or "guillotine" into YouTube to see great clips.
The last advice is to watch a lot of wrestling matches on FloWrestling:
Wrestling - Flowrestling | Wrestling Videos, News, Results, Athletes, Coaches on Flowrestling Again, make sure at first you are watching only HS matches so you don't get confused on rule differences. You will enjoy watching the wrestling, but really focus on what the referees are doing -- where are they positioned, how do they move, how do they signal, how do they communicate with the wrestlers, etc. You will learn a lot just by observing what good officials do.
Other than that, all I can say is have fun. Wrestling is a terrific sport and it is a great experience being part of it out on the mat.