Can you imagine walking around all day with your shoes being two sizes too small, your nails overgrown and improperly cared for, and with rocks and mud all under foot? Not appealing, is it?
Your horse’s feet require proper care and for that you need to make sure that you regularly take your horse to a proper farrier. When the horse’s hooves are split, the shoes are rusty or nails are coming loose - it's too late; the equivalent of you waiting to go to a chiropodist until your feet are cracked and destroyed.
Each horse requires its own specific hoof care routine, this means you have to arrange a regular, scheduled appointment time for your horse to visit the farrier to have their specific needs taken care of.
Horses need their shoes for a variety of reasons; to protect their hooves and allow normal growth to take place if the wear is quicker than the regrowth - likewise you wouldn't want to walk over sharp rocks without your shoes, also there are times when a horse will require additional traction for pulling and finally you have cosmetic reasons - if your horses gait is off then you may wish to speak to your farrier about corrective shoes to improve the walk and to prevent any skeletal problems from arising.
When you are choosing your farrier be sure to ask around for recommendations from other people who you know - make sure that your shoe specialist is experienced in dealing with the specific problems that your horse may or may not have. If your animal has no specific options then you will still want to make sure that your expert is, in fact, an expert in your type of horse - here I am not talking about the breed as such but more the function that your animal carries out. A dressage horse and a working horse will have very different farrier requirements and you will want to make sure that your horse is within their range.
If your horse is already lame then do not leave it to suffer; make an appointment with both the farrier and your veterinarian immediately. Once your horse has, hopefully, made a full recovery you are going to want to make sure that this doesn't happen again.
Remember this is a regular routine that you want to develop - take your horse to a farrier the way you would change your own shoes!