Let's start with a short nail anatomy lesson. At the end of each toe -- your dog has four per paw -- you'll find a nail. Depending on the dog, the nails may be dark, light or a combination. The “quick” is the fancy name for the blood vessels and nerves that grow through the center of each nail. The tip of the nail has no nerves or vessels and is safe to cut. However, if the quick is cut, it's a bloody mess and your pooch is in pain.
Some dogs have "dew claws," which are extra nails loosely attached to the inside of the leg a few inches above the front and/or back paws. Most dogs have one on each front paw, but some breeds, like the St. Bernard, Briard and Norwegian Lundehund, often have dew claws on their rear legs or even double sets of dew claws. Dew claws never contact the ground and, therefore, require frequent clipping.
I recommend that dogs have their nails trimmed about once a month. This rule, of course, varies by the individual dog and his genes and lifestyle. Obviously, the more active the dog, the more likely the nails will be naturally ground down and fewer trimmings will be needed. Once you hear the tell-tale clickety-click of nails on the floor or concrete, you'll know it's time for a pet-i-cure. For Mr. Magoo and other handicapped dogs, older dogs or pooches that stay inside or walk on softer surfaces, I recommend more frequent nail trims, perhaps even every two weeks.
It is the rare dog that requests a pet-i-cure and it's often difficult to see the quick and, thus, accidents happen in an instant. Therefore, I always recommend that people take their dogs to a trusted professional groomer or veterinarian for nail care. Professional nail care is not typically expensive and it will save you and your precious pooch a lot of pain and suffering.