Using the proper leash and collar can help make your dog training successful. Most pet supply stores carry a wide selection. Following are the more common types of leashes and collars:

• The common flat leash and buckle collar are available in leather, nylon and metal chain of various lengths.
• A retractable leash, much like a fishing pole, lets a pet wander up to 20 feet ahead, while still under your control. Pushing the button takes up the slack. (It’s not a good choice when teaching an animal to “heel.”)
• A head collar, also known as a head halter, looks like a kind of muzzle. Attached to a leash, its function is to stop pulling and keep a dog under gentle control via a loop around the mouth, as well as a collar around the neck. It doesn’t restrict the mouth; rather, it thwarts lunging by transferring the forward motion into a sideways head turn. This type of lead is especially effective on energetic or difficult-to-control dogs, but because of the noseband, it can’t be used on dogs with short snouts, such as pugs.
• A harness, designed to stop pulling, wraps around the dog’s chest and shoulders. The leash attaches to a ring on the front of the dog’s chest. As with the halter, the idea is that when the dog pulls, it will be turned to the side. Be careful when shopping for harnesses, as some attach to the leash on the dog’s back rather than the chest, which can exacerbate a pulling problem.
• Choke and prong collars, when attached to leads, control dogs by tightening around the neck or jabbing the throat with spikes. You pinch and release for the corrective action and quick attention, not to choke the dog. These are not for novice handlers and can be dangerous in inexperienced hands. Many trainers don’t recommend them because they cause pain and can injure a dog’s windpipe, neck or spine. Should they get caught on something, or if the chain isn’t threaded through the rings correctly, the dog can choke to death, because the collar continues constricting even after you’ve released the tension on the leash. Check with an expert for instructions before using.

Warning: Never use a choke collar on puppies; dogs without thick neck fur; dogs with a respiratory problem; or breeds with fragile windpipes, such as Chihuahuas or Yorkshire terriers, because you could easily injure your dog.

Primary source: Iams.com