What do you mean when you asked for what you should look out for? Are you talking about the settings such as shutter speed, aperture, light, etc or anything special to shoot? If you are talking about the latter, there are certain poses which are quite nice, and you can try taking high flying stunts. I think the process of coaching can be quite interesting too.
first thing you're looking for, is to UNDERSTAND the sport.
the more you go spend time watching the sport, the more you'll understand - i didn't know anything about iceskating until i had a chance to know a new friend who's working at the rink. then i made it a point to start to pay attention to the different moves during the sport, as well as the various skaters. anyway, i'm still learning from my failed exposures, wrong compensation, lousy framing etc. the same process was repeated with canoepolo, you can see my selected shots from a recent canoepolo competition at http://forums.clubsnap.org/showthread.php?t=58922 of course, it helped that from the first time i shot canoepolo in aug 2003, i had already gained a fair number of acquaintances and friends, that helps in candid shots if that's what you're looking for.
similarly, what you CAN do, is to spend time reading about the particular martial art, or just spend time with the group of people you are with. if by any chance you are already part of the group, but want to take photos of your teammates, you're already halfway there, since you know what kind of moves to expect.
this seems to be the time when digital comes in handy... lol but my 2mp mavica jsut dun cut it... good thing is that its held in a controlled enviroment... but the room is really small and the place crowded.. bout 50 person in a 6x5 tatami room.. scared ppl keep flying into my line of shots..
from your shots, seems like the best is to go with shallow DOF? uhm.. can give it a try... hope my ang bao can cover the expenses... lol thanx sehsuan