action photos?

[photoguy]

I am a sports photographer who has been asked by a referee to photograph him officiating a game. These images would go into his portfolio/application to move up in levels.

My question to everyone here is: What is looked for in this type of a photograph? What are the desirable traits to demonstrate in the photos?

This post is not an advertising attempt, but one to get credible information. I am struggling to locate reference manuals in my area to look at. Any help would be greatly appreciated.

Thankyou.