If it's an open 3 point tournament. Meaning 3 points and you win. Don't bother using your rear leg. In this style of sparring it's all about speed not much power. Your going to be using your hands more, particularly the backfist.
Usually when they throw a back fist, they follow up by turning it into a high block then using a reverse punch.
Sometimes they start thier attack with a lead leg side kick, followed by high back fist(to the face), turn the back fist into a high block and follow up with a reverse punch to the stomach. You will see this attack alot.
Warning: Becareful sometimes these tournaments can turn into boxing matches, since it's all about speed sometimes they turn into boxing matches. And punches are thrown with no regard for control.
If your a TKD stylist it will probably be difficult for you to score with your legs, since the hands are quicker. From my experience this kind f sparring is like a "tag game" first person to touch gets the point regardless of how ineffective the attack was.
Remember back fist is the most commmon attack so prepare to high block it, sometimes competators may leap at you with crazy jumps just to tag you with a backfist.
"Poor is the pupil who
does not surpass his
master" - Leonardo Da