To be able to shave off valuable seconds in a jump off you will have to be able to keep your horse straight and jump at an angle. This simple exercise will up your skills and help your horse feel comfortable with what is expected.
Put one fence in the middle of the arena, as shown above. make the fence jumpable from both directions with a ground pole on each side of the fence. Keep the fence at a comfortable height to suit you and your horse. This is not about the height of the fence, this is about being able to pop the fence at an angle.
Begin this exercise at trot. Follow the green arrow. Ride a figure of eight at a 90 degree angle to the fence. Jump the fence a few times. Start cutting the corners gradually, making sure the horse is straight at all times when jumping. Continuing onto canter, the horse should at this stage of the training be straight for at least 2 strides before the fence and 2 strides after the fence.
Do not fall for the temptation to flex the neck of the horse towards the fence, this will give the horse an opportunity to disengage the front and run past the fence instead of jumping it.
Keep the horse between you leg and hand, make sure you are centered over the horse.
Continue to decrease the angle as shown in picture (orange and red arrows). A word of warning, do not try a smaller angle that you are perfectly comfortable with. If your horse rund out, start at the beginning.
Is your horse continuously running out?
Are you only ably to manage to cut the corners a very small bit before running out becomes an issue? Bring this exercise down to the very basics. A pole on the ground! Bring pole work into your daily routine. Practise leg yielding, make sure you have all the controls in order.