There are so many great resources available to help you with training or learning about judging. Check out some of the links below:
https://www.theretrievercoach.com/ Kevin Cheff Retriever Coach
Retrievers Online – Dennis Voigt https://www.retrieversonline.com/articles
Judging Fundamentals and Check List
Drills Handbook – Published by the Labrador Retriever Club of Greater Boston
Dobbs Dogs – Training Tips for Retrievers
Retriever Field Trial Judging – A Manual by Pete Simonds (the American blue book), Retriever News online store
https://www.eliteretrievers.com/ Pat Burns, Elite Retrievers Training Program