If its point sparring its not very strenuous. Basically you attack or your opponent attacks until you get a point. Doesn't take long anyway in my matches. So its like start, stop, start, stop, start, stop. Lots of little rests.
Breaking is the most fun! (in my opinion, I love it) You get all the stress from the forms out - on the boards. If you are a lower belt, gold, orange, white, you really have an advantage usually. It depends if your "class" group of people you are subdivided in at the tournment. If you decide to do some breaks, don't practice during the week before, at least nothing to get sore. When I was a white belt, I did step side, and palm strike. If you are have more mass than me 145 lbs then you might possibly do two boards palm strike, if you have practiced it. At each tournament, I upped the techniques to get a little harder and I usually did the breaks I had already accomplished at testing for the belt and added on from there, or my master would suggest some. Breaks like front, axe, knife, hop side are good for beginners too.
As for form, you usually go to the judges table when your name is called, say your name, my school is....., my instructor is....my form is Taeguek 1 or whatever it is (ask your master) and then you say with your permission may I begin. Then you go backwards from the table to the starting point of your form--allow yourself room so you don't get to near the judges table. Then when you are in joonbi position, they will say begin or see chuk. Have Fun!