Crate training has long been recognized as the preferred method for both potty and obedience training with dogs. From personal experience, it has been invaluable in training my out-of-control terrier mix not to soil inside my apartment and to keep her from destroying items around the house while we are not around.
In simple terms, a crate is nothing more than a means of confining a dog to a small area within your home. If done correctly, the dog quickly learns and accepts the crate as their "home" and often prefers to lay around inside the crate even when you are still there.
The major benefits of crate training your dog are as follows.
1. REDUCED PET STRESS: Dogs are known to be more comfortable and relaxed when in a "natural" home environment, i.e. a "cave," which the right type of crate readily replicates. When dogs are left out and about while you're gone, they feel responsible for the protection of the entire household, and often this can be very stressful for a dog. On the other hand, if they are crated, dogs will worry only about their immediate surroundings and what they can affect, which is the environment inside the crate. This takes the pressure of protecting the home away from them.
2. EASIER TRAVEL: Crates can be used with ease when moving, traveling, or visiting others as "mobile homes" to calm your dog and ease the transition - dogs will use the crate as a comfort tool that is familiar and safe for them. The familiarity of the dog's own home can allow them a safe retreat when the rest of their surroundings are new and scary. In addition, crates are great for the travel process itself, as dogs will be happy to ride around inside them, and the crate is easy to move from place to place as needed.
3. POTTY TRAINING: Crates are excellent tools in potty training your dog. A dog's natural instinct is to never soil their primary "home," since in the wild the smell would have attracted unwanted visitors. This fact carries over to crate training, where a dog will think long and hard before soiling in the crate. You would really have to "push it" with how badly the animal has to go and how long you have been gone from home, which ideally you would avoid doing anyway. Once you are home, and they are released from the crate, dogs will understand that it's time to go outside and do their business. Make sure you reward them when they do this correctly.
4. CONTROL: Crates help establish a control factor and promote your status as the dog's pack leader. By crating your dog, you are stating "I am in control of your life." Your dog is not threatened, but rather comforted, by this pack structure, because they understand that you will protect them from harm. Dogs must have a pack leader at all times, so if you fail to take control of their lives, they will do it for you in a natural attempt to take over as the leader.
TYPES OF CRATES
I would recommend the plastic variety, since they block out more light and dogs seem to be more comfortable inside. They also contain any possible clean-ups inside the crate, rather than allowing spillage. The metal "cage" variety is an alternative, but I've found that their plastic bottoms are easy to chew through; they can be flipped over, and are easily opened even by a small dog. Some companies also offer aluminum or other metal crates that are practically indestructible, an alternative if you have a particularly chew-happy dog. Sizing is important, since a crate that's too small will be uncomfortable, but one that's too big will not be a good potty training tool (a dog can use one corner as the toilet without too much thought). Attempt to fall somewhere in the middle between the two extremes. If you are training a puppy, there are dividers available so that you can purchase a full-size crate to start, and allow the pup more room as it grows.
Finally, remember that although a crate is a home, your dog needs plenty of exercise and interaction with you during the day - it's not meant to be a prison. Enjoy & love you dogs, and they will bring you many years of happiness.