The right length
Make sure your stirrups are the correct length. For flatwork, the stirrup iron should be level with your ankle bone when your leg hangs beside the stirrup leather. If, however, you are having trouble keeping your seat or rising to the trot, you might benefit from shortening your stirrups a hole. Always shorten your stirrups by at least two holes for jumping.
It’s a ball!
Have your stirrup on the ball of your foot (the widest part). This allows you to have supple ankles, without them getting locked, which can happen if you just have just your toe in the stirrup.
Sticking-out toes = v bad!
Toes should face the front. If they stick out, your knees stick out, too, and the wrong part of your leg is next to your pony. Plus, you may get swept off your pony if you go through a narrow gateway!
Too much toe?
As you ride, glance down at your toes. You should just about see the very tips of your toes. Any more and your feet are too far forward. If you can’t see them at all, check that your feet are not too far back.
You hips, knees and ankles should all be supple, and open and close as your ride. Think of them as well-oiled hinges.