Turning On The Forehand
Do a quick warm up at the walk, trot and canter.
Stop in the middle of the arena (where your helper should be).
Decide which way you want your horse to turn his hindquarters towards(these directions are for if you're turning the hindquarters to the left).
Bend your horse's nose to the right side ever so slightly.
Put your right leg behind the girth and keep contact with your right rein.
Your partner now can reinforce your leg by putting his or her hand on your leg and pushing his hindquarters with his or her other hand.
Once the horse moves, praise him and reward him by taking all pressure off.
If the horse does not respond, you can give him a little tap beside your leg with the dressage whip
If the horse moves forward, back him up to where you were and keep a little more contact with your reins.
It is better if you teach the horse this on ground first without a saddle. Use your hand to ask and if it does not work, reinforce with the dressage whip.
This is not for a green horse who does not know what leg pressure is!
Do not immediately lose your patience and start hitting the horse if it does not respond right away; these things take time.
These are just guidelines--remember, not all horses respond in the same way.
Taken From Wiki How