If you have a large breed, manage it’s growth and exercise. Don’t let it get overweight, as that increases stress on the joints. If the dog has any joint abnormalities, get on a excellent glucosamine/chondroitin/MSM supplement, like Glyco-Flex III or Synovi G3, as early as you can. These supplements are more effective before the arthritis starts, and can delay it’s progress. The earlier, the better.

If you are thinking about buying a dog, make sure you go through a reputable breeder who does all the necessary health testing on their stock for joint issues common in their breeds. With larger breeds, this is usually hip and elbow dysplasia. In toys, patellar luxation. Dachshunds, spinal issues. A well-bred dog is less likely to have the joint problems that lead to arthritis.

Exercise helps keep dogs in excellent health–and lubricates the joints too.
Dogs can take omega3 and 6 fish oils as a supplement–also glucosamine/chondroitin as a supplement.

here is a detailled link–all about the various types of canine arthritis, prevention, treatment, etc;
http://www.recoverysa.com/arthritis_pro.htm

I suggest giving raw chicken wings about twice daily. A BARF diet works even better, though. And just like with people, exercise can keep your dog younger for longer. So, make sure the dog isn’t overweight, and take him on walks more regularly.

And, well, arthritis is one of those things that may happen no matter how much you work to prevent it. It basically depends on the dog’s genes.