Crate training

Dogs feel secure in small, enclosed spaces. A dog crate makes an excellent and safe place for your puppy to stay when you're away or when you cannot watch him. Choose a crate where he has enough room to stand up, turn around and lie down. Dogs do not like to eliminate where they sleep or eat. However, if you get a huge crate for a small dog he may do so in one end and sleep in the other. If you have a puppy that will grow into a large dog, you may need to buy two different crate sizes or purchase a crate with a divider you can move as he grows. If you can’t get a crate, place your puppy in a small-delimited area like the kitchen or bathroom. Most Shar Pei puppies does not tolerate crates very well. For them, it is better to use a puppy proved enclosed area.
Use a single-word command for your dog to enter his crate, for example, "KENNEL"; throw in a treat when the puppy enters, praise him and close the crate door. Increase the time he spends in the crate before you let him back out. Remember, your dog still needs time to play and eliminate. Maintain a regular schedule of trips outdoors so as not to confine him too long.
If your puppy cries non stopping, leave him alone. Wait until he calms down, even if it takes hours, just be very patience.  After he has been quiet for about 1 minute, come back and give him lots of "good boy"/"Good girl", take him/her out, etc. Your puppy needs to understand that screaming is not the way to call for attention. He/she will get attention independently of his behavior.
Your dog can stay in his crate comfortably for as many hours as many months old  he is, plus one month (2 month old pup + 1 month = 3 hours in his crate). Following this rule, there should not be "accidents" in the crate.
If you stay away from home for 9-10 hours a day, then be prepared to clean the mess, and give your puppy quality time as much as you can. If you stay away from home for more than 10 hours a day, then you should not have a puppy. You should wait for the correct time or consider to get and older puppy or adult dog.
Always take your puppy outside to the same area in your backyard to eliminate on a leash so you can praise him when his job is finished. This will take the guesswork out of his visits to the backyard.
For how long does the puppy needs to be in the crate when not supervised? Puppies have to earn their freedom. The moment will come when you have stopped to say "no, leave it" or "drop it" all day long. Leave him roaming free for short periods of time, and the increase them.
Most Labrador female puppies can reach this point at 1 - 1 1/2 years of age. Male Labrador puppies should reach this point at 2 - 2 1/2 years of age. Shar Pei puppies should get to this points at 10 month to 1 year of age.