The Match

At the start of the match, you are supposed to walk straight out to the edge of the match and bow before stepping in-bounds.  You go and stand behind a little red line near the middle of the mat, and you will see your opponent standing behind his or hers a few meters in front of you.  The referee will call "hajime", or make some kind of grunting noise that sounds something like this, and you start to play.  You are supposed to try to throw your partner flat onto his or her back to win, as explained above.  Simply keep trying to do this.  If you both end up on the ground without a match-ending throw happening, then try for a pin, and even submissions.  The referee will call out various things to the time-keepers and score-keepers, which don't involve you much.  Just keep fighting until you very clearly hear the referee call "matte", which means "stop".  He or she will call this if there is no-progress on the ground, or there are penalties to be given, or after the match is declared over, either through Ippon score, or through running out of time.  You don't need to worry youself with 'why' he or she calls "matte", you just need to know that it means "stop", that's it.  You will hear "hajime" if you are to continue fighting.  Besides the common sense fact that you shouldn't intentionally go out of bounds, there is not much more you really need to know in order to fight in a Judo tournament.  If you want, you can look up at the score board to see how many Waza-aris and Yukos each of you have.  Since you can win at any time though, with an Ippon throw, pin or submission, the scores don't always matter all that much.  You'll have seen quite a few other matches already before you end up getting your chance that day anyways, so you'll 'get it' by just seeing what everyone else has been doing.