Steps
1. First groom your horse. Click to learn how to properly groom your horse. Grooming first will make it easier to wash him, plus, it'll make him even cleaner.
2. Put him in the wash rack, and safely cross-tie him or use a quick release knot. Rinse one side of his body, starting at the legs. Make sure to check the water temperature. Don't spray his face unless he's ok with it, the water temperature is good, and the hose sprayer is at a gentle setting!
3. Lather your horse with shampoo. Start at the neck and work your way down using either a curry comb, a medium bristle brush (my favorite), or a scrubber designed for washing horses. Be gentle when scrubbing the legs and do not scrub the face!
4. Wash his mane. You may need to use a stool for this. Use only your hands when washing the mane and tail.
5.Rinse. If your horse's coat feels slippery, rinse more. Make sure you rinse the belly, where all the soap falls to, extra well.
6. Repeat steps 2, 3, and 5 for the other side of the horse. 6. Rinse & wash your horse's tail. If his tail is a light color, leave the shampoo in for a few minutes before rinsing it clean. This will whiten and brighten it (or you could buy whitening shampoo).
7. Wet your sponge, put a dab of soap on it and cautiously wash off your horse's private areas. Rinse. Yeah, it's gross, but it's even grosser to leave it dirty. :P 8. Give your horse a final all-body rinsing to be sure that the soap is all off him. 9. Wet a rag and gently scrub your horse's face and forlock with it. Don't use soap, because if it gets in his eyes, it'll sting! If you do use soap use very little, and be sure to rinse it off well.
10. You can optionally condition your horse's body. I don't really recommend it, for it doesn't seem to do too much. Conditioning the mane and tail, however, is beneficial. Put some conditioner in your hands and hand comb it into the mane and tail. Leave it on for a few minutes, then rinse.
11. Now use the sweat scraper to help dry your horse off faster. Use a towel to dry his head and legs.
12. Spray the mane and tail lightly with conditioning spray. HAND comb through so you don't break the hair.

Don't ever turn your horse out or put him in his stall while he's still wet. The first thing he'll do is roll. Trust me, I've experienced this before, sadly. :) If you have to put him in his stall, either give him a flake of hay, put a light sheet on him and a tailbag in his tail or tie him (unless you will not be present).