Here is my advice.
Buy the Redding Study Guide
https://thatsitideas.com/doublesdist...onlineform.htm cuz it is awesome. Read it, highlight it, and work as many games as you can.
Go to a clinic or two if you can and any on field stuff at a clinic is a bonus.
This board, and the NF board,
http://www.nfhs.org/scriptcontent/va...?ubb=forum;f=9, is a great site that focuses on NF FB. You can learn from reading, looking in the rulebook for answers, posting, and asking your own questions.
A mentor is a great way to go if you have someone who is good and will work with you. Talk to him about things as often as he will let you, via email or phone.
Start watching games and thinking of what the signals and enforcements for fouls that you see happen are before the official comes on and does the signal and enforces the penalty.
HAVE FUN AND NEVER STOP LEARNING OR STUDYING!!! GREAT TO HAVE YOU ABOARD!!
Grant's site has a ton of good stuff.
http://home.comcast.net/~minnmo/football.htm