If you want to compete its makes a lot of sense to know the rules as well as you can. Here is a great video to aquaint yourself with the basis of the rules and point system, its good viewing for understanding exactly what is happening with the scoreboard and what the referees hand gestures mean during competition.
Another set of vids with more details and more informal verbal descriptions:
This one is pretty good for explaining negative points, advantages and general naughty things you should not be doing! Infact if you have time, have a little trawl through his account because the vids are quite helpful but be warned he does talk a lot!