To teach a standardbred horse to race is a matter of taking the horse's natural inclinations and expanding them. Instead of trotting or pacing through the pasture with its herd, it will be expected to get onto a track with rivals, pull a two-wheeled cart and trot or pace faster than every other horse on the track.
Feed the young horse a quality diet high in protein to aid in the development of strong bone and muscle. The horse should be fed a veterinarian recommended ration split in half and fed twice daily. Start this diet when the horse is a foal and adjust the diet for its different life stages according to your veterinarian's recommendations.
Harness break the horse. This is done in stages and teaches the horse to wear the harness that is required for standardbred racehorses. Start small with one piece of harness at a time and allow the horse to see, feel and become used to the harness. As its confidence builds, attach the traces and hobbles, if you're using these, and let the horse wear them until it no longer notices or is bothered by things smacking and touching it all over.
Ground drive the horse. Use long reins attached to the bit and walk behind the horse, driving it and asking for turns left and right, stops, starts and back ups. This can be done both in and out of the harness. Use a whip to desensitise the horse to sounds and tickling, snapping it in the air around the horse until the horse has no reaction. Touch the horse all over with the lash until it is unconcerned.
Hitch the young standardbred to the sulky, the two-wheeled racing cart it will be pulling. Proceed carefully so as not to frighten it. Work in an enclosed ring so if the horse does become frightened and bolt, there is less chance of injury. Lead the horse pulling the sulky, then graduate to long-lining the horse around you in a circle until the horse is comfortable with the feeling of pulling the cart.
Get in the cart when you are sure it is relatively safe to do so and when you are sure you can adequately control the horse and take it out on the track or on a very quiet road to practice and train.
Condition the horse to be a racehorse. This means working the horse out often through training and speed conditioning. Training the horse involves jogging it to build stamina and speed conditioning the horse involves trotting or pacing it over various distances to expand its lungs and build muscle. The best way to train a standardbred racehorse is to carefully balance training, speed conditioning and downtime to recover.
Every horse and every trainer is different. You should not attempt horse training without the proper experience and knowledge of horses; young horses can be dangerous and unpredictable.