Get a vet check yearly. Get all of the required puppy vaccinations, and keep him vaccinated for rabies, and follow your vet's vaccination protocal. Use heartworm preventative.
Feed a quality food. Go to www.petfoodanalysis.com and pick a 5 star or better food. Keep canned pure pumpkin on hand to feed a couple of tablespoons if dog has diarhea. (If it doesn't clear up in a day or so see a vet).
Make sure dog always has access to clean water.
Walk dog twice a day for 20-45 min depending on breed/fitness/age.
Learn what items are toxic to dogs (plants, food, chemicals).
Keep home puppy proofed to prevent dog accidentally eating items that can cause a blockage.
For old dogs add a glucosamine, chondroitin, MSM supplement. Also add a fish oil pill daily.
Groom dog daily and check for ticks.
Never let dog off leash unless in a safe fenced in area.
Microchip your dog. Keep address/ph info updated.
Keep ID tags on your dog.
Spay or neuter unless you can be 100% certain the dog will never be outside unsupervised, or where it can breed.