That depends on the dog and your relationship with it. If your companion animal is easy to handle, and you know how to clip the claws, you can do it yourself. But if a dog isn't being cooperative or doesn't like to be restrained, it is best to let a vet or a groomer do the job.
If you do the manicure at home, you've got to be very careful not to cut too close to the quick, the living part of the nail that has blood vessels and nerves. If you cut into this area, you'll cause the dog pain and see some bleeding, and that probably will be the end of the session. The quick is easiest to see on light-colored claws. It can be hard to see the quick when claws are black, so you'll have to estimate where it begins. Try drawing a line with a felt tipped marker around each claw, a safe distance from the tip, and not going beyond that when you clip.
Make sure you have a nail clipper designed for dogs (and know how to use it) before you attempt a manicure.
When dogs are able to run or walk out of doors on rough ground, their activity keeps nails naturally polished so that claw clipping may not be necessary. Also, the claws on the back feet usually are shorter than the ones on the front feet so you don't have to clip them often.
You can find demonstrations and photos of dog nail clipping on line. If you've never clipped your pooch's claws before, it's worth taking a look at the pictures or getting a lesson from your vet or groomer.
Andrew Weil, M.D.