I started judging at Regular last week, and one thing that made me uncomfortable was watching players break rules. Sometimes the opponent would look at me like, "Are you really going to let this happen?" I tried my best to educate the players without providing an unfair advantage or being a pesky judge who intervenes every thirty seconds, but I'd rather have a set of official rules that I can follow so that I know when to intervene.
For example, one player declared an attacker, the opponent declared a blocker, then the first player declared another attacker, and then the opponent looked to me for intervention. Not sure if I should intervene, I decided to ask the player, "Do you have a question?" He took the bait, and I was able to correct the situation and educate the players on how declaring attackers works.
When should I intervene in a match?