by  Mitzi  Summers
The three “Golden Rules” of horse training are “Calm, Forward and Straight.” Your horse needs to be relaxed and confident as you train him. In this way he will be receptive to your aids and will be able to be “in the moment,” not concerned with flight or fright, but able to respond and allow you to use positive reinforcement techniques. “Forward” enables your horse to be in front of your leg, responding to a whisper of your leg or seat to encourage impulsion. A nervous horse galloping with his rider, only responding to painful pulls on his mouth and not by barely visible half halts, is not truly forward. Forward is controlled impulsion, and it can be demonstrated even in a rein back. 
Straightness takes many years to achieve if indeed it is ever really successful. The definition of straightness itself is often misunderstood. It does not mean, of course, that you can ride your horse in a straight line across a large field. The horse needs to be ambidextrous, equally supple in both directions. Unless doing lateral work, the hind legs should step into the track of the front legs.
Whether going through a corner, or traveling the length of the arena, your horse should be able to be as strong and supple on either side. Balance and true collection can only be obtained when the horse is straight. Each exercise performed correctly will equally improve the elasticity of the horse’s back and joints, and increase the carrying power of the haunches.
It is quite common to see crooked horses at lower level dressage classes and open shows for pleasure horses or hunters. If you observe a horse from above, you will see that he is built a bit like a triangle; the haunches are a bit wider than the shoulders. When ridden close to an arena wall or a fence, horse and rider alike have the tendency to hug the perimeter, keeping the length of the horse the same distance from the barrier. If the shoulder and haunches are the same distance, the result will be that the horse is crooked, with his haunches more toward the center of the ring. This will result in unequal balance and mobility of the body of the horse and interfere with the final desired goal of straightness.
To correct this tendency, it is necessary to move the horse’s shoulders in front of the haunches by performing a shoulder-fore. The shoulder-fore is a precursor of the shoulder-in, perhaps the most valuable lateral schooling exercise. For shoulder-fore, the rider’s inside leg remains at the girth to keep the horse from moving his entire length sideways. It also maintains impulsion. The rider’s outside leg will be lightly behind the girth. Using an outside bearing rein and a directional inside rein should result in a slight feeling that the horse is “lifting” as he moves his outside shoulder over, a bit like the feeling of the beginning of the turn on the haunches.
You can teach your foal to move away from pressure merely by preventing forward movement with a light hand on his halter (not a rope halter which can cause serious poll inflammation), while lightly pushing with your fingertips or knuckles where your leg will eventually be applied. Ask for one step at a time and three steps for each side is enough. Do not ask for displacement of the haunches while twirling a rope at the side of the animal. This will not be a clear request for your horse and will not led naturally to the final desired result. It is a threatening gesture, far from exact to elicit a specific number of steps, and also frequently results in the raising of the horse’s head and stiffening of his back — all undesired reactions.
If you are working with an older horse, I still like to teach the initial lesson from the ground. If I am working with a student, I will first ask the horse in the same manner that I used on the foal, then merely have the rider take over when the horse understands. It usually takes just minutes, but if your horse does not understand maintain patience and do not drill him. Go on to something else and repeat every so often.
The turn on the forehand teaches the horse that he can move laterally from a leg aid — that if a signal that usually requires forward movement now adds a restraining aid from the rein he is to move laterally away from pressure. It also teaches him to wait for signals from each side as in the turn on the forehand he is placed in a bit of a “box” between the rider’s legs and hands. The movement does place the weight of the horse on his forehand a bit more, and therefore does not belong in a dressage test. It is still a necessary step in the horse’s training and should be included. It will be quite useful in opening gates and maneuvering at mounting blocks or trail classes.
I like to teach the horse to leg yield next, after he understands the turn on the forehand and can perform 15-meter circles fairly successfully. One method used to teach the horse to yield to the leg is to put his forehand toward the wall or fence of the arena at about a 40-degree angle. I rarely use this method as it takes the “forward” part of leg yielding away as it is performed in dressage tests. I also find that it often makes a horse initially resistant as it is more difficult in this manner. Initially the goal is to teach your horse that he can move forward and sideways, so that I may simply ask the rider to ride further away from the corner of the ring and then simply ask the horse to yield his barrel slightly sideways. He is already a bit “softer” on the inside. It is important that the rider can recognize when the horse’s inside hind leg is just beginning to become ungrounded for a forward step, as this is when the inside aid must be given.
When the horse understands the movement forward and laterally, then start the exercise in straight lines. You can use poles on the ground spaced so that the horse keeps the inside of his body next to the outside of the poles. Their placement encourages him to move sideways while keeping his body straight. Often a horse will start to move his shoulders too far to the outside, thus losing the efficacy of the movement. When this happens, simply half halt and go back to your shoulder-fore exercise. Remember to half halt your horse whenever he needs to be rebalanced.
Now you are starting exercises that truly help the horse begin to strengthen and make more flexible the joints in his legs, strengthen his back and soften his neck and poll.