UNDERSTAND THE INTENT OF A RULE
As you read a rule, stop and think about the "intent" of the rules makers. Understanding the logic in why a rule was adopted will assist you in enforcing the rule. Many times the intent is obvious, such as player safety. In other instances, it is there to ensure that neither team or participant gains an unfair advantage.
Knowing the intent of the rule will result in better judgement, and make you a better official.