Instructions
Determine what the problem is. Many young horses will buck and release sudden bursts of energy due to playfulness, not malice. Horses confined to a stall and not given much turnout might behave in the same way. There are other breeds of horses that have what are called "hot" temperaments, meaning they are more prone to excitement than other breeds. You must know the horse you are working with, and understand that his age, breed, personality, feeding program and exercise schedule all play a part in how he acts.
Calm your horse. If the horse is afraid of something unrealistic (a flapping plastic bag), assure him by using a low voice and patting his neck. This simple gesture can calm your horse immediately. The saying "If you aren't worried about it, he won't be either," always holds true. A calm horse is less likely to explode and exhibit poor behavior (kicking, biting, bucking, etc.).
Use a crop. If you are riding and ask your horse to move forward, he should immediately step away from the pressure. If he does not, a tap from the crop on his hindquarters will help him to understand that leg pressure means go.
Say "no." Especially when working around your horse on the ground, a sharp "No!" often remedies the situation. For example, if your horse lefts a leg to kick or tries to bite you, saying "No!" loudly makes the horse understand that you are in charge, not him.
Back the horse. If the horse does not respect your space, move him away from you. Backing a horse that is disrespectful during groundwork makes the horse understand that he must stay where you put him.
Get the timing right. When disciplining or training a horse, no more than two to three seconds should lapse between what the horse does and when the correction is applied. Horses learn by repetition, but only when they can relate to what you are asking for.
Reward the horse. Horses learn by pressure and release. If you want your horse's mouth to be soft, begin to release as soon as your horse accepts the bit. If you ask the horse to back up, stop asking as soon as he is in the spot that you want him to be. It also goes a long way when you pat and speak kindly to your horse. Horses have keen memories and senses--a gentle but firm trainer will get better results over the long run than someone using brute force.
How to Discipline a Horse
Horses are amazing animals. They are strong, intelligent and eager to please. When the equine you are working with acts up, there are several things to consider and many ways to remedy the problem. Disciplining your horse depends upon his temperament, why he acted up, how far along he is in his training and how much trust you have gained from him. Horses must trust their trainers, and being harsh never works. On the other hand, you are dealing with a very large animal. It is imperative that you establish your status as the herd leader and remain his leader throughout your relationship.