There are many types of dog collars out there, and the best type for your dog depends on the size, breed, and training requirements. For many dogs, a traditional nylon or leather collar is perfectly fine. Such traditional collars come in many colors and sizes, and should ride high on your dog’s neck. A traditional collar should be snug, but you should be able to fit two fingers in between the collar and your dog’s neck. The weight and width of the collar depends on your dog’s size; if you dog is big, go larger, and vice versa.
Other types of collars include harnesses, chain slip or “choke” collars, and halter type collars. Harnesses go around your dog’s neck and shoulders and behind the front legs, and are best for dogs with upper respiratory diseases because they release pressure on the throat and trachea. Choke collars, when used appropriately, are useful for training dogs who have not responded to leash training with traditional collars. If you use a choke collar, have a trainer show you how to do it to avoid injury to your pet, and make sure the collar is only used during training sessions. Halter type collars will give you the most control over your dog. These collars look more like a horse’s harness and give you control of your dog’s head.
Works cited:
http://www.drsfostersmith.com/pic/article.cfm?aid=159