It definetly all starts with the diet. Make sure your walking dog has a high protein diet with little or no "broken grains". whole rice is fine, preferably brown, but things like corn meal and ground barley are not good for dogs. Sure they did eat grain eaters, but only 10% of energy is transfered from the grains the deer ate to the wolf that ate the deer.
If you're using worm medication make sure it also protects against tapeworms, there are two kinds in the pet trade ones that do and ones that don't. Keep a bottle of fish oil and throw some on their food once a day, this helps to create the kind of enzymes that directly benefit skin and fur.
Dogs do live in a "pack oriented" mindset, whether it be with humans or dogs. So the healthiest thing you can do for your dog is obedience train. tricks like roll-over and high five are fun but hold no value when your dog charges at a stranger. If i would recommend one book on dogs it's "How to be your Dog's Best Friend" by the monks of New Skete. They have been training german sheperds for hundred of years. It contains great insite on how your dog views you. We often personify dogs and as if they think , though limited in grammar, similar thoughts to humans like "Do you have food for me mom?" when really its more like "food?food? outside? run?" so learn to recognize you dogs metal status. remember that if you died in the woods your dog would just walk off into the trees in search of a new pack, be it with other wild dogs or humans.
When it comes down to it, your dog looks to you for everything. And most of the time you can tell what someone's homelife is like just by hanging out with their dog. My favourtie one is the "Child-Protector". When a dog becomes over protective of children. This usually stems from that "pack" mentality, there are certain jobs in the house and they all need doing. If a dog senses that you are not doing your job as a parent, or a poor job at it, they will take over the responsibility. As long as your dog knows you have control over ever situation, and respects you for it, you should have a happy life together.
oh, and if your hitching with your dog, try to minimize the "head out the window" time. exposure to high velocity winds can cause ear and eye problems in dog.