About a stride out, allow your hands to just relax, by then you can't do anything and it's the horses job to do the work there. This will help your release over fences which will also help your overall position. Sit up and do not drop your shoulders into your position and lean on the horse, the horse should be jumping up to you, your body will naturally come forward into the proper position. Your hips should take in most of the action, and allow yourself to stay down until the horse lands as you do not want to come up to early and pull on them. As for your leg, keep your calf tight against the horse, and put your weight into your heels. Do not pinch with your knees as this causes your lower leg to swing. Allow your body to follow the horses movement, it usually comes naturally, don't force yourself into a jump position too early.