They should be tested every spring for heartworms and placed on a heartworm preventative from May to December.
They should have yearly fecal exams for intestinal worms and treated accordingly.
Unless you are a experienced breeder with a thorough knowledge of your breed's bloodlines and screen for possible genetic defects and are willing to be responsible for every puppy your dog produces, your dog should be spayed or neutered. Bitches are at risk for mammary cancer if left intact and males are at greater risk for testicular cancer unless neutered.
Dogs should be fed a good quality dog food. If you change foods, gradually mix the two foods together to prevent a gastric upset. Dogs should not be free fed. Obese dogs are not healthy dogs.
Your dog should be groomed regularly (once a week); with special attention to ears, teeth, eyes and toenails.
You should seek veterinary attention if your pet shows signs of illness.
If you can not provide this level of basic care, you should reconsider pet ownership.