Showing your horse love and companionship is the most important part in taking care of your horse. Without your horse feeling love, he/she will not become attatched to you.
When horses are young, their mother shows them love by groming them. They would help clean their mane and their body. By grooming your horse, you are showing him/her love and companionship. Sometimes, if your horse loves you, he/she will try to turn around and clean you hair!
By giving your horse attention, you are showing him/her love. Playing with him/her in the pasture is another good idea, although some horses will just want to graze.
When riding, lean down and give your horse a pat on the neck if he/she does good.
Your horse shows that he/she loves you by following you!