For each heat there is a team of judges, 7 in total with 5 judging at a time and 2 rotating. This team sits in the judging tower, so that they can see everything that is going on out in the water. The judging team is always international, unbiased, with vast experience (they judge over 700+ waves during the ASP tour alone), and leading this team is the head judge. The head judge's job is to oversee everything, to make sure that the scoring is fair, that all the timings are spot on and that no waves or maneuvers are missed etc.
Once a heat has begun between two or more surfers, it is the first wave that sets the precedent. After this wave has been scored, all waves that follow will be compared to that first wave.
Each surfer's wave is scored out of 10, and the score is based on what the surfer does with the wave. The level of difficulty, the maneuvers, the power, speed, flow and their commitment determine what score the surfer will receive. Each of the 5 judges will award a score out of the possible 10 points. To reach the final score the highest and lowest scores are removed, and the remaining scores are averaged out. Here is the grading:
ASP heats work on a two wave combination. The surfer tries to achieve the two highest scoring waves in order to defeat their opponent. There is a maximum score of 20 out of 20 points available. During a heat a surfer is allowed to be scored on up to 15 waves, yet only the two best waves will count.
Depending on where a competitor finishes in an ASP competition there are points on offer. Whether a surfer is knocked out at round 1 or succeeds in winning an event, points are awarded. Here's the breakdown of what each round/heat offers:
Contest win/1st place 1200 points
Round 4/9th 600
Round 3/17th 410
Round 2/33rd 225
Round 1/33rd 225
So there are the basics of how a heat is judged and scored. There are numerous minor rules that the ASP keep in place when it comes to determining wave priority, interference and even scoring maneuvers, yet what it comes down to is the best man of the heat winning, regardless of popularity or reputation.