There is much to learn by watching this little video showing a puppy being crate trained. I am a strong advocate of crate training, and it's something I think we should continue even after housetraining, etc.
Having an adult dog who is comfortable being crated for a few hours allows you to travel very easily with your dog (we just got back from a wonderful trip to Santa Barbara and our 3 dogs slept in their crates in the car each night. Other times, we've rented a ski cabin in Lake Tahoe that normally doesn't allow dogs, but the owners agreed to in our case because our dogs would be safely snoozing in their crates during the day while we skied, and the owners knew there would be no destruction to their second home.
In the event of a disaster, having a crate-trained dog is essential. It allows you to keep your dog with you, safely confined in a crate, sheltered from the chaos and instability of its physical surroundings.
Lastly, it allows other people to care for your dog in your absence. If your dog refuses to be crated, how do you expect your friend to care for it for a weekend and be sure it won't escape the yard trying to find you? Staying home all weekend personally supervising the dog is just too much to ask. The dog should be safely confined unless it's out of the crate on leash being walked, played with, and personally supervised. This prevents dogs escaping due to confusion over where its owner went.
OK, so here's the video. Notice how she points out what specific aspect of the behavior she is rewarding, and how the behavior is broken down into tiny steps. I also love how the crate is in her bedroom. Puppies need to sleep in crates in the bedroom. That way you can hear them if they have to go (for adult dogs, you can hear them if they have an upset stomach and suddenly need to go). I'm not a fan of dogs in the bed, but I am a fan of dogs in the bedroom.