First the stirrups must be set at the correct length for the rider. A good way to gauge length before mounting is to measure the length of the stirrup leather and iron against your arm. Make your hand into a fist and place your knuckles against the stirrup bar then pull the stirrup up under your arm. If the bottom of the iron reaches right up under your arm then this is approximately the correct length.
Once on the horse the rider must sit in a balanced position to help the horse remain balanced underneath and move naturally.
The rider should sit in the lowest part of the saddle, allowing the hips to open and for the legs to move back and lie gently around the horse so that the heel of the foot is directly in line with the hips. The ball of each foot should rest on the strirrup iron with the toes pointing fowards and the heels pointing down.
The upper body should remain straight but not stiff with the head looking foward. It should be possible to draw a straight line from the shoulder to the hip to the foot of the rider.
The upper arm should rest by the body with the elbows bent, allowing the forearms to become an extension of the reins.
To hold the reins correctly, face your hand face down with your fingers pointing towards the horse's neck, place your little finger under the rein and the other fingers over the rein and the thumb underneath. Curl your fingers around the rein and then turn your hand so your thumb is on top and your knuckles are facing foward.
It may be difficult to maintain this position at first, especially once moving and you may find that your legs creep forward, or you may be tempted to grip with your knees if you feel unbalanced.
If you feel unbalanced or feel you are losing the correct position it is often best to move to a slower pace, reposition yourself correctly and then start again rather than to continue unbalanced as this only serves to make it harder for both horse and rider to relax and work together.