The main issue with either surfing or bodyboarding is that it is primarily a subjective process and depending upon who the judges are and what their level of experience and expertise is, certain things might be judged more critically than others. That being said, surfing and bodyboarding are close to the same when it comes to wave selection, position, board control, etc.
http://surfing.about.com/cs/surfinst...10404judge.htm lists some of the basics but if you have a chance to talk to Dave Dalkewicz at Ocean Atlantic surf shop in OC, he's done training for a number of the delmarva esa judges.
For one, I place a high priority on wave selection and positioning. Depending upon the wave and the conditions, the most critical part of the wave is tight in the curl (tube) and your ability to maneuver in and around that area with skill, control and finesse. Needless to say, lacking control like falling off or getting hammered will rarely win you the highest point values, but pulling off an especially appropriate maneuver at just the right position and moment in the wave can get you very high points. The main difference with bodyboarding is the type of "stunts" or "moves" if you prefer. Surfers don't do "stunts" unless you're into big air- and those only count if you can pull it off with a solid landing. Again, there's a lot of subjectivity, but the best thing for you to do is to watch someone who is generally considered a VERY good bodyboarder and study his or her techniques and wave positioning. On my judging card, excellent control and critical positioning at critical moments in the wave always trump a cheap stunt- especially if you don't pull it off.
As an afterthought- connect with a professional bodyboarder like Jay Reale and get his opinion on it. I'm sure he'd be willing to share his experience with you, and he has considerable experience between he and his pro bodyboarding wife Vicki.
http://www.ebodyboarding.com