It's possible to remove just a few porcupine quills from a dog's skin using a pair of needle-nosed pliers. However, if a dog has multiple quills sticking in his skin, a trip to the veterinarian is a must because he may need to be anesthetized or otherwise sedated during removal.
When pulling a quill from a pet's skin, it should be grasped near its point of entry and pulled out in a straight motion. An antiseptic should be applied to the location, and it should be topped off with antibiotic cream. A follow-up visit to the dog's vet to ensure that infection does not set up in the resulting wound is a good idea.