The yearling horse should receive much of the foundation he needs to grow into a safe horse that is a pleasure to be around and work on. If you raised your yearling from a foal, your path to teaching him these basics is typically easier since you know his history. If you've recently acquired him, assume he's a blank slate; moving slowly and calmly, gauge his experience with the basics of haltering, leading, grooming, tying and trailering.
Reinforcing Desirable Behaviors
If your yearling hasn't had much handling, he's operating on instinct; that is, he's a prey animal and you're a predator. Everything will be scary to him, so move slowly, calmly and deliberately. Never, ever raise your voice or react out of anger; you'll just be reinforcing your role as a predator and thus something for him to fear. If he's trepidatious about you approaching, use food, such as alfalfa, to reward him every time he allows you to get closer. Don't push it -- reward small incremental improvements rather than just the final goal. Operate as though he's a weanling who has just left his mother. Keep sessions short, even just 5 to 10 minutes a day. Once he allows you to touch him, you can reward by scratching and rubbing him.
Don't feel bound to just one session with your yearling per day if he's inexperienced; a routine of two brief sessions a day gives him the routine he needs with a break in between.
Understanding Release from Pressure
Once you can touch your horse, work on touching him for longer periods, eventually leading to a light restraint. If he starts to walk away, go with him, keeping your hand on him. As soon as he stops, remove your hand as one reward -- you're releasing the pressure of your hand. Follow that with the reinforcement of a treat or gentle stroking.
Introducing the Halter
Haltering your yearling is a goal, but think of it as a process rather than a single event. Begin with an introduction; let him sniff and smell it. Rub it on his nose and other places on his head. Break down the haltering process so that by the time you slip it around his nose and head, he's so familiar with the equipment that he has no reaction to it. Once he's haltered, introduce him to the lead rope by rubbing it all over his body. Once he has no negative or surprised reaction to it, attach the lead rope to the halter and further reinforce the pressure-and-release concept by gently applying and then immediately releasing the pressure as soon as you feel him "give" to it. This sets him up for future lessons on tying and leading.
Haltering your yearling is much easier once you can touch him all over his head, including his nose and ears.
Familiarity to Touch
Your horse is going to be touched throughout his life, some of which will be comfortable and other times not so. Catching, haltering and introducing the lead rope are just small starts. He'll need to tolerate brushing, bathing, saddling, veterinary exams and having his feet trimmed and possibly shod. However, you don't want to hurt yourself in the process. Yearlings are like active teenagers that weigh several hundred pounds. Use a stick with a rag attached or a similar extension of your hand that allows you to rub his entire body. Don't forget his stomach and along the inside of his legs. Once he no longer reacts to that, you can continue that training with your hands and work on picking up his feet.
The Yearling Colt
If your male yearling hasn't been castrated, you could experience a burst of energy when his hormone production begins. Usually this happens in the spring after his first year. Ideally, you'll have been able to establish many of the handling basics during the winter, when you'll typically not notice any difference between him and any other horse his age. Use this extra energy to your advantage by setting up a regular exercise program with him. The key to working with intact colts is to keep them busy and focused on you.
Stud colts are typically extra sensitive about being touched in certain areas, including legs and feet, so be prepared to spend time getting him used to your touch.