continuation...
After a few weeks have passed, the horse will begin feeling confident, at which time increase the pressure. Work the horse in a big circle to avoid injuries. Once the horse learns to hold a trot over several laps, begin using voice commands to urge the transitions between walk, trot and canter. Responsiveness to the voice commands becomes very useful later when riding begins.

Once the horse retains the trot with regularity, execute the transitions, a little walk and canter attached to the lounge. This introduction training prepares the horse to accept the riding equipment (bridle, saddle, lateral reins, etc).
The lateral reins must be loose at the beginning so as the young horse can stretch its neck to feel the contact. Gradually tighten the reins conscious that the horse neither frightens nor tenses. The reins must permit the horse to advance without any problem. At the beginning, the lateral reins are useful to control the horse, to provide balance, and to begin shaping the body. Begin to form the spine, or top line (persist on shaping the spine for the first year of training). If the reins are adjusted too short, it can damage the horse, if too high only the neck is worked when the objective is to exercise and shape the entire body.

After finishing with the lounge work, flex the horse’s neck for a few minutes. It is important that the upper line of the ears is parallel to the ground. Some horses do not require flexing because they are naturally disposed, but with others, it is necessary, especially with the ones with a robust frontal built.

At this time, start accustoming the horse to the weight of a rider by hitching-up gently on one stirrup and the other, until the horse is mounted from both sides with ease.

Lunge work with a rider (Minim. 1 month)

After building up a good base, it is time to start the under saddle part of the training. Complete a lesson on the lunge then continue working the horse in the hand, but this time with a rider on top. This exercise is excellent because the person in control of the horse is the one leading from the ground, and the young horse slowly gets used to the weight of the rider.
The following day, if the horse is confidence and relaxed, start a slow trot on the lunge with the rider holding on to the mane or a dickey. For the first few days, the rider should refrain from holding the reins because the young horses could get scared, the control of the horse comes from the trainer on the lunge.

continuation...

The objective during this critical period is for the horse to become accustomed to a rider’s legs and voice. Caress the neck every time it follows a command. Better to English trot the horse, when sitting on the saddle do so gently.
Once the young horse is comfortable with our weight, he is relaxed and with works with regularity, it is time to hold the reins.

The work on the lunge with the rider is very important as it balances the young horse; teaches it to curve the neck, make correct transitions, launch into a canter, make direction changes, etc.

At this juncture in the training, the problems a horse may have are detectable. This is the best moment to start solving them.

In addition, at this stage, the young horse is worked in the entire ring (without a rider) with saddle and lateral reins. Three persons stand aligned in the center and make it work both hands, to make circles, diagonals, etc. This work accustoms the horse to the walls of a ring.

The first days mounted in the ring it is important to prevent it from stopping to stretch while in forward motion. One way of preventing this bad habit is to use an old horse as a guide. These two ways of starting a young horse has proven to render good results.

Routine of the young horse under saddle
From the beginning it is important that the young horses learn to wait, to stay still. When mounted, it is common for a horse to become anxious, therefore the trainer must remain strict to correct the natural impulse and only mount when the horse stays in place, then wait a few minutes before advancing forward. Little details influence the future development of a horse. 

Once the young horse is accustomed to working with a saddle, slowly start reducing the minutes on the lunge and increase the amount of time riding him.
Also, start riding trails. One day a week trail riding is good for them and does not disturb training on the ring.