1. Keep your dog in good weight.
Compare your dog to the descriptions and pictures in the Purina Body Condition Chart. If you are in doubt about your dog's body condition score, ask your vet during your next visit.
Ideally you want your dog's ribs to be palpable.
A good way to understand what palpable means is the following. Make a fist. Now run a finger over your knuckles. This is what ribs on a dog that is too thin feel like. Now open your hand, and again run a finger across your knuckles ... this is what ribs on a normal weight dog should feel like. Now turn your hand over, and feel the flesh just below your fingers. This is what ribs on a dog that is overweight feel like.
If you find that your dog's ribs and waistline aren't where they're supposed to be, adjust the amount of food that you are feeding.
Of course the best method to use to watch your dog's weight is periodic weighing. I weigh my dogs twice a month, record the results, and adjust their food accordingly. I use a Ohaus Catapult C11P9 Scale which I like because of its "dynamic weighing mode" - I press a button, an LED counts down five seconds, and I am given the average weight over that five seconds. I purchased mine from Old Will Knott Scales.
See also the web site of the Association for Pet Obesity Prevention.
2. Brush your dog's teeth daily.
The build up of plaque on your dog's teeth can lead to peridontal disease, which can lead to heart disease, kidney disease, liver disease, and other problems. You feel yucky if you do not brush your teeth; no doubt the same is true for your dog.
Remember to only use tooth paste formulated for dogs. (Human toothpaste will upset your dog's stomach.) An alternative to a toothbush is to use a dental swab that wraps around a finger and you rub against your dog's teeth. (I use Drs. Foster amd Smith Dental Clens Pads.)
See the website of the Veterinary Oral Health Council (VOHC) for products (treats, toothpaste, etc.) awarded the VOHC seal. (I regularly use the Healthy Mouth water additive, and as very special treats feed my dogs Greenies.)
On the advice of my dental vet, twice a week I give OraVet Dental Hygiene Chews to my dogs.
3. Annual dental exams with dental x-rays.
Many dog "experts" recommend annual "wellness exams". But more critical are annual dental exams and cleanings, beginning between six and eight months of age. If you do an annual dental exam, you will get a "wellness exam" as part of the process.
Even if your dog's teeth are pearly white, dental disease can hide under the gum line. Make sure your vet is taking dental x-rays; otherwise find a vet who does take dental x-rays to do the dental. Annual dental exams are recommended by the American Animal Hospital Association ()
Many dog owners wait until they see significant tarter on their dog's teeth before they have their dog's teeth cleaned and examined. The usual result is that some of the dog's teeth need to be pulled. Instead of following such a strategy, one dental specialist () points out that we would cause our dogs less pain and suffering over the course of their lives if we extracted all the teeth in their mouth. (Teeth are not needed to eat canned dog food and small kibble.)
See the website of the American Veterinary Dental College for more information.
The topic of spay and neuter is controversial. Since my dogs are not allowed to roam freely, I control the sex lives of my dogs. So the original justification for "spay and neuter all dogs" - animal control - does not apply. (In Europe where dogs are not allowed to roam, dogs are not routinely spayed and neutered.) So then the decision becomes one of health. For the best review of the scientific literature on the subject that I have been able to find see this blog post on Evaluating the benefits and risks of neutering dogs and cats by the SkeptVet. Without a compelling medical reason, I do not neuter my male dogs and I wait until my female dogs are older (near ten years old) before spaying them.
You must be the health advocate for your dog. Ask questions of your vet and feel free to say no.
Many dog clubs offer health clinics where various health tests are offered at reduced rates. You can find out about local clinics at the following web sites:
 Whole Mouth Extraction For Everyone, Dr. Fraser Hale, DVM, FAVD, DiplAVDC, Jan 2016 CUSP.
Last updated 20180123.