As Matt and Kay said, your first step is to have your horse on a good feeding program, that can be a large part of how your horse looks and feels. You can get dry skin in the winter, so can your horse! So a coat supplement, such as ground flax or super 14,Dac, etc. will help your horse keep his bloom and not be dry and itchy this winter. Good quality protein levels for the age and use of the horse are so important. Note I said quality, try to buy the best quality feed you can afford for your horses. Good quality hay helps as well too along with good clean drinking water.
We also try to start conditioning our horses 90 days prior to the first show if possible. Start them out slow and easy, it will take a bit to get them used to being worked and their muscles developing. We start out at just five or six minutes each direction then add a minute every other day to their time. We work our horses normally five days a week, sometimes six if one is behind. We normally increase their workouts to 20 to 25 total minutes depending on what type and how hard the work out is and weather factors, it gets pretty hot here in the summers. I feel like working them 20 minutes maintains the muscle you have, pretty much, more will increase your muscle in your horse, but dont overdo the workouts. So working up to around 25 minutes is a good amount of time. We both trot and canter our horses. Cantering will help tuck up the underline of the horse better, but do a mix. Watch your horses respiratory rate too, that will give you a good idea of when he is worked enough too. We do sweat our show horses with throat sweats and neck wraps too. Some have them on now but they are Always taken off when the horse is turned out. We use neoprene neck sweats to work them in, sometimes layering them or using plastic underneath once spring comes. Its important not to leave them on too long after working, they can blister the horse so keep a close eye on them. Usually you would be safe to leave the neoprene sweats on a good 25 to 30 minutes after working, then take them off, rinse the horse, being sure to get in the area behind the front legs good and let the horse dry before putting on the throat sweat and neck wrap again. I do let my horses have a couple of hours with it off to let them dry out. Sometimes on their off day I will let them have it off too to air out some. Sweats most effective with continued use.
We start our horses of course first learning to lead and tie well if they are not used to it already when they come in for training. Then we teach all horses to lounge (except weanlings) so that in the case of being at a show and needing to work one they will already know how to do this. It also teaches them manners and to Whoa when asked and stop and wait for your directions on what you want then to do next. Once they learn to lounge well then we free lounge them in the round pen or larger area for excercise. Our round pen has a couple of dump trucks of crushed limeston in the bottom all packed down really well, then two dump truck loads of wood mulch (not shavings) on top of that. It is very cushiony on their legs and spongy feeling to work on. It also is good footing for them, not slippery. Once they are working well, then we may move them to working on the hotwalker which has sand in it about four inches deep. This also helps to muscle up the shoulder and gaskins well. Our hot walker is larger in diameter since its a large horse walker that has had the arms let down some, the larger circle is better for the horses so they are not turning sharply all the time. If you dont have a round pen, then a paddock will work, hopefully not one so large that is would be hard to work them in freely and keep them going, but not too small, as you dont want the horse constantly turning in too tight a circle all the time. Once the horse is very confident in working and used to voice commands, and everything going around them, I start training them to work beside the golf cart. This needs to be done in a very safe manner, starting them out slow and easy.Start them out walking, then slow trotting, back to the walk, turning, real easy. They will learn to know the sound of the motor too, and you can cluck to them when wanting them to move on a bit too, especially when they are first learning. You can get them in a good canter and faster trot later when they are calm and confident in this workout. I like this workout best because I can determine easily how long I want them to trot, canter them up an incline, or slow down to a walk to get a breather or walk the last part of their workout to cool them down. I see the most progress with with this workout in their conditioning. You must keep an eye on the horse all the time though to be safe, never tie them to the rear where you cant see them. We start out just wrapping the lead around the arm piece and holding on to it, in case the horse gets upset we can loosen them up quickly. Most horses really enjoy this workout the best because they get to go out into the field and see the scenary while working, they seem to love it once they learn it. I always keep the horses in view when working them. Also you dont want to have your lead too long either as they could get a foot or leg over it. Most important, teach your horse to lounge and round pen and have him pretty well started before attempting to put him next to a golf cart. Always use safety for the horse foremost, know the area where you will be working him too, making sure the surface he will be working on is free of holes or other hazards, and take your turns slow and gradual. IN this workout the horse is not turning all the time, especially for yearlings. Take into consideration the age of the horse too, a yearling may not be able to work as hard as some of your older horses. Work each horse as an individual, some will need more than others. Most importantly constantly check your horses weight, you may need to increase or decrease a bit during the season too. If they have a belly but are too light in weight on top, you actually need to increase their grain. All horses need hay to help them digest their food, long stemmed is best in my opinion, but if you feed hay in cube forms or use it as a supplemental hay then soak them first well to avoid choking.
You will need to evaluate your horses condition regularly and you can increase or decrease your workout a little bit accordingly. Consistency in working your horse is paramount. He will need some time off though, and a bit of turnout will help to keep your horse happy and attentive as well. We turn our show horses out in the early morning or late afternoon, early evenings, so they wont get sunburned as much for a little while once they are started back in training.If your horses has just been clipped, this is important as they can sunburn easliy. REally be careful of close clipped legs and white areas that are clipped close as turning them out in strong sunlight will turn these areas too pink.
We turn them out a lot though in off season,and let them just be horses. Most of the show horses are up in stalls at night though so that I can still feed them separately and keep them on their show feed. During winter we do give them a bit more hay than during show season, they need the extra roughage and it helps to keep them warm in winter cold months. I think its important to do this and let them play and relax in off season, you can still keep them pretty close on their weight while doing this in this manner.