If you have a dog, and you live anywhere except maybe right in the middle of a city, chances are, your dog has met up with a porcupine. This is a common occurrence with dogs, especially hunting dogs. Most cases of porcupine quills are not very serious. Usually the dog receives them in the face and front paws. If the dog has an abundance of quills, or they are located in his mouth, it is best to get him to a veterinarian, who will anesthetize him, and not cause him further pain and stress.
Most cases of quills can be removed at home without the cost of a veterinarian, if you know how to do it properly. First, you may have to muzzle the dog. Some dogs will know that you are actually helping, and welcome your efforts. Still others may get defensive. Just be safe and muzzle your dog if his actions call for it.
Pour some plain white vinegar on the areas where he has been stuck with quills. This will help to loosen the quills. Next, snip each quill with a pair of scissors. This will let air inside, helping to loosen the thing. Then, with a pair of pliers, pull the thing straight out. When all the quills are out, check in hidden areas, like between his toes, under his chin and under his ears for quills you may not have seen.
This is not a very comfortable thing for your dog to have to go through, so remember that if he starts getting irritated. Do not get angry at him, he is probably scared. But, keep yourself safe and muzzle him if you think he may snap or bite. Make a trip to the veterinarian if needed, and be on the lookout for quills or pieces of quill that you may have missed, which may show up in the form of a limp in the next several days.