TRIM

Start with a correct and appropriate trim. Here are the basics:

Balance the hooves - the heels should be even when viewed from the bottom.

Reduce excess toe length and flares, but respect the white line of the hoof. 

Trim heels no lower than hard sole. When in doubt - leave it!! Don't try to lower very high heels all the way in one trim - you'll have a sore horse. A 30 degree hairline (viewed from the side while the hoof is fully loaded) seems to work well, but it may take a few trims to get there. The horse will appreciate it if you take your time.

Frogs and bars should be slightly passive to the  ground  and taper towards the frog apex. Avoid over trimming these structures!

Remove only dead, flakey sole. You can't carve out concavity if it doesn't exist yet! Avoid invasive trimming. On thinner soled horses it's best to leave things alone. There is always the opportunity to trim more in a few days if needed, but you can't put it back once it's gone. Hint: take the horse for a walk on gravel if you aren't "sure".

Nutrition

Horses do best on a mineral balanced, high fiber diet containing adequate protein. Avoid molasses and  high fat, high starch commercial feeds. Feed a grass hay based diet. Beet pulp is a safe way to add more calories if grass hay isn't enough. Green pasture can be dangerous for some horses due to the high sugar content. The closer you stick to what nature intended a horse to eat, the healthier your horse will be. Whenever possible, have your hay analyzed (or buy it from a source that does this) and correct any mineral imbalances or deficiencies. If your horse's hooves are in poor condition, take a close look at his diet. In northern California our forages tend to run high in iron, but deficient in copper, zinc, and selenium. In my own experience, putting horses on an appropriate mineral supplement, such as California Trace , has yielded excellent results in hoof strength and overall good health.

Terrain

Horses evolved as herd animals covering considerable distances over varied terrain. Their hooves will adapt to their living conditions. What does this mean for a barefoot horse? If you horse lives in a soft paddock, then that is what his hooves can handle when you go out to ride. Don't expect a barefoot horse to trot down a gravel road if he hasn't been living on a similar surface with plenty of room to exercise. Hooves need a conditioning program just as much as muscles do. You can do something as simple as moving the water trough as far away from the hay as possible and placing a good layer of road base gravel in the commonly traveled areas of your horse's environment. Provide as much formal exercise as you can if your horse is confined to a small area. Hoof boots can allow your horse to travel comfortably in conditions, such as gravel and rocks, which his hooves are not conditioned for. I recommend Easy Care Gloves and Epics,

"A horse is that thing of beauty. None will tire of looking at him as long as he displays himself in his splendor."
Xenophon
photos on this page by Sally Hugg