As said above, for your turns and try to keep moving. You loose seconds if your horse stalls on the turn. Also, I find that 'opening the gate' a little with my reins help to keep my weight to the inside, whilst concentrating on not leaning too far forward.
And PLEASE sit quietly. Not flapping your arms and not flapping your legs help your pony keep its balance and run faster. I watched the local rodeo on the weekend and only one girl rode her horse quietly and despite the fact that she knocked a barrel (her horse slipped) she was still the fastest by half a second (before penalties).
Only As Old As You Feel - Sometimes I Feel VERY Old