from http://coxscorner.tripod.com/scoring.htm here are the four keys to scoring a round
a) Effective Aggression
The key to the first category is the word "effective." One may be going forward, trying to get at ones opponent, forcing them back, but not throwing punches, or missing badly. In order to be "effective" one must have success landing consistently while moving forward. It should be noted that the opponent, who is "out-boxing" or keeping the fight at a distance, can be the "effective aggressor" by initiating the punching exchanges.
b) Defense
A badly over-looked aspect of boxing, especially in scoring a fight. Defense is a part of combat. In boxing it is the ability to hit the opponent without being hit in return. Defense may include ducking, dodging, bobbing and weaving, parrying, blocking, slipping, and sidestepping, as well as effectively utilizing the clinch.
c) Ring Generalship
The person who dictates the tempo of the fight and controls the action in the ring is the ring general. The boxer who makes the other man fight his fight. If fighter A keeps the fight in ring center, and nullifies the "aggression" of fighter B he is the better ring general." Or if fighter B effectively cuts off the ring and forces fighter A to the ropes where he can go to work he then is the better ring general.
d) Clean and Hard Punching
This should be obvious, but it's not. Since many fans and sportswriters ignore the two previous categories they often fail to understand what is actually taking place in the ring. A "clean" blow is one that lands flush without being blocked by his opponent. But how many times has one heard an announcer "Oh what a left hook by so and so!" The problem is the punch landed on his opponent's glove and only made a loud noise and didn't score at all. Some blows are "partially blocked"; meaning it did not land with its full force. Such blows are not "clean" punches. Also it is not the amount of punches that are thrown the matters, but the amount of blows that land. Hard punching is important as the amount of damage a blow causes counts in the scoring. In the amateurs a knockdown is only as good as a jab, but in the pro's its worth much more. One hard right that staggers the opponent though is not worth ten hard jabs that snap back the opponent's head. Damaging blows and their value are difficult to assess and that is why boxing is subjective. However it should be noted that landing 3 or 4 punches that hurt an opponent in the last seconds of a round are not enough to make up for losing the first two and a half minutes of the round where he was out-boxed. After all the name of the game is boxing not slugging!