Preventing getting kicked by a horse should be quite simple if you follow these basic rules and apply some common sense!
Most importantly, always assume every horse kicks and use caution anytime you are near the rear half of a horse. Next, is a matter of common sense; ask the horse’s handler if the horse has kicked in the past. If so, you either use extra caution and stay away from the back half of the horse. Depending on how bad the horse’s kicking ‘habit’ may be, and your experience level, you may want to simply avoid that horse.
When you approach a horse, keep a calm demeanor and voice, talking to the horse to ensure he is aware of your presence. Approach from the front or somewhere between the shoulder and head. When working around the rear area of the horse, always stay very close, keeping continuous contact with the horse.
This contact can be keeping your hand on the horse, running it down its body, where ever you are working with the horse. Contact can be also be maintained by keeping your shoulder or body ‘brushing’ up against the horse. This is especially effective when walking around the back of a horse. By maintaining continuous contact you enable the horse to know it is still you touching him, even when you are in his blind spots. This also prevents nervous horses from ‘jumping’ each time contact is made.
Staying very close to the horse, especially near the hind legs will prevent the horse from kicking you as hard, if he were to kick. When there is some distance between you and the kicking legs, you will more likely get kicked at the horses' 'full swing' than be fast enough to jump out of the way in time. Up close, the horse can still kick, but it is more of a bumping or banging into you, as opposed to a full bore kick.
Remember that horses spook and react on instinct (fight or flight, and fight means kicking). You are not the only inspiration for your horse to kick. Watch for what is going on around you; dogs, kids, and other horses. Keep a safe distance away from the rear of other horses, do not ride where horses are loose (pasture), and ask other riders to maintain a safe distance behind your mount.
NOTE: Children should avoid walking around the rear or passing underneath a horse; have them walk around the front of the animal, please!