You obviously should know the rules inside and out, with a lot of extra study on penalty enforcement, all-but-one, and the exceptions. That's the easy part.
My feeling is the WH's biggest job is the crew. You should have worked and should know the mechanics of every position - and know them well.
You should stay up on changes and improvements in in the officiating field by reading a lot (like this board, Referee Magazine, other publications, etc.), attending clinics, presenting info at your local meetings, etc. and pass your knowledge on to your crew - and to other officials.
Get to know the assigners, the ADs, local coaches, etc. so you get a new perspective on the game. As the WH, you are the expert. As I also tell my crew, the honor of wearing the white hat goes to the best looking and smartest guy on the crew. For me, being the smartest took the most work.
