The law that decides whether a game flows. How to signal it, how long to hold it, and the one question that tells you it's over.
Advantage is the law that most separates a good game from a stop-start one. Get it right and the game flows; hold it too long and you're managing a penalty nobody remembers; blow too early and you've punished the team that was wronged.
The principle is simple. When an infringement happens, you can let play continue if the non-offending team might gain from it. The hard part is knowing when that gain has actually happened.
Signal early, decide late
Put your arm out the moment you see the offence, and call it so the players hear it. Then give yourself a clear question: has the team that was wronged done something with the ball that's better than the penalty would have given them?
If the attack gets over the gain line with numbers, or kicks to touch well downfield, that's advantage. If the pass goes to ground and the defence scrambles back, come back for the penalty.
Advantage is a decision, not a delay.
Log every advantage you play. Over a season, the pattern of when you came back, and when you didn't, is the fastest feedback you'll get.