For a dog that enjoys regular outdoor activity, nail trimming may not be needed. In many cases, walking on pavement maintains a dog’s nails at an acceptable length. However, there are steps to take to ensure nail trimming isn’t an unpleasant experience for your dog:
Before you ever attempt to trim its nails, begin by touching its legs, feet and toes, and associate this with an activity it enjoys. When it is resting, begin petting it, gently passing your hands over its back and legs. If this is well tolerated, you may wish to give it a small food treat. Do not try to do too much the first time.
Gradually manipulate your pet’s foot more each time. Eventually you should be able to slip your fingers in between each toe, gently squeezing each one to flex the nail, putting gentle pressure as you hold each foot and manipulate the leg. Do not attempt this when your pet is feeling agitated or playful.
Once your pet tolerates having its feet touched during quiet times, you may begin to incorporate this into elements of play time. Train your dog to assume a “down/stay” position when it retrieves a ball, for example, and “shake” its paw before continuing the game.
Make sure not to cut into the quick, or the living portion of the nail bed that contains sensitive nerves and blood vessels. That is a painful experience for the dog, and he’ll begin to associate the trimming with bad things. If you are unsure how to trim your dog’s toenails, ask your veterinarian or technician to show you how. The nail bed is seen as a pinkish triangle at the base of a nail; however it may not be obvious in dark-colored nails.
There is more variety between the shape of toe nails in dogs than in cats. Some pets’ nails grow in a more curved shape as compared with those growing more parallel to the ground. This may determine how short they may be trimmed. Even a skilled professional can misjudge the depth to which a nail may be trimmed.
It is better to cut less than to cut more than necessary. Trim off small sections at a time and stop well short of the sensitive portion of the nail. Cut your pet’s nails frequently, a little at a time, rather than occasionally when toe nails are uncomfortable to both your pet and to you.
Source: "Canine and Feline Behavior Problems," Stefanie Schwartz