Not all dogs can be left alone in a house. Thankfully, one of the purposes of crate training is to limit your dog's access to your belongings if he can't be trusted not to shred, rip or chew. The most common use of dog crates is house breaking, or house training. Dogs don't like to go to the bathroom in their private den, which is what the crate is supposed to simulate. They're also a safe and convenient way to transport your dog if he doesn't do well on car rides.
Choosing a Crate
The crate you select should only be large enough for your dog to stand, sit and stretch. If you buy a large crate for the dog to grow into, block off one end (many crates come with barriers). Plastic crates, sometimes called "flight kennels," are used for traveling and give the dog less visibility. Collapsible metal crates are cage-like, with a plastic tray bed. Other collapsible, rigid crates come with fabric covers, limiting the dog's visibility to the room around him. Some animal shelters rent out crates, which is beneficial if your dog is going to grow significantly.
Before your dog will want to sleep in his new crate, he'll need to become familiar with it. Put the crate in an area of your home where you and your family spend a lot of time with the dog. Put something soft inside for him to curl up on and keep the door open. Some dogs will take to the crate as a den without encouragement. Others will have to be coaxed inside with treats and toys. Make sure nothing on the crate hurts or scares the dog, like the door swinging shut.
Feeding your dog in or near the crate will help him associate his new dwelling with a positive experience. Some dogs will be ready right away to eat with his bowls all the way in the back of the crate. Others will have to grow comfortable with it gradually. With each meal eaten inside the crate, lengthen the amount of time you leave him in it afterward. Don't be sneaky about shutting the door, or he won't trust you or his new crate. Once he doesn't mind staying in there for 10 minutes or so, teach him to go in the crate for longer periods. A command, like "crate" or "kennel," can be used to order him inside, and when he complies, he gets a treat. Increase the time he's crated and the amount of time you're out of his sight, and once he's mastered being alone in the crate, you can leave him to run errands or to sleep through the night.
Especially with young puppies, it may be best to keep the crate in your bedroom or very nearby, because he'll probably have to go outside during the night. Keeping him close means you'll be able to hear his whimpers. Older dogs should be kept close by as well, as they could associate the crate with isolation. Once he can sleep through the night, the dog can be moved out of the bedroom and a little farther away. Your ultimate goal is for your dog to feel safe and secure inside his crate, not abandoned or trapped.
If your dog is whining or crying while being inside the crate, don't immediately attend to him. Likewise, letting him whine for an extended period of time and then letting him out won't help, either. Wait for your dog to stop whining for 5 minutes or so before giving him any kind of result. He shouldn't learn that whining is a ticket out of the crate. If you can't tell whether he needs to go outside or just wants out of his crate, use the words you use to indicate going outside and see if he responds. If his whining becomes an uncontrollable problem, you'll likely have to restart your training. Don't try to use the crate as a cure for your dog's separation anxiety; as anxiety is linked with destructive behavior, the dog may injure himself attempting to get out of the crate. If your dog's anxiety issues don't subside, you may need to consult a veterinarian or behavior specialist.