Unlike your hair, which grows all the time, a dog's fur grows in spurts. In nature, these spurts are determined by environmental and seasonal changes. Domestic dogs, on the other hand, are exposed to irregular light and temperature patterns, like central air conditioning, which may make your dog's fur grow sporadically and somewhat unpredictably. However, that doesn't mean that you can't help her fur grow healthy. Helping that coat grow in a healthy, beautiful fashion requires a combination of treating your dog outside and inside her body.
Feed her a protein-rich diet. Dogs require protein for their muscles, growth and energy, as well as their fur. If yours doesn't get enough protein, her skin and fur will suffer, drying out and losing their healthy sheen.
Give her food with omega-6 and omega-3 fatty acids. These fats are perfect for encouraging healthy coat growth, making the fur grow thick and strong. It even alleviates skin problems, like dandruff, so make sure that her food is formulated with these fatty acids by reading the label or asking your veterinarian. If you don't want to disrupt your dog's diet, you also may administer supplements formulated for dogs.
Bathe your dog only as much as her breed dictates. Some dogs must be bathed more often than others, and bathing your dog too often can be bad for her coat and skin. A dog's body produces natural oils that spread throughout the coat and make it healthy, and if you bathe her too often, you strip out all those healthy oils -- and her coat suffers the consequences.
Brush your dog's coat regularly. Keeping her coat clear of dead fur prevents buildup and matting, which don't necessarily stop the coat from growing more, but are unhealthy and problematic nonetheless.