Chewing for a puppy or dog is a natural behavior.  It is a way for the dog to keep its gums healthy and teeth clean.

The problem is what the dog chooses to chew on.  Many people think that it is a fun game to allow a dog to "play rough" when it is young.  Suddenly the dog is an adult dog and what we try to express to clients is it only takes breaking of the skin and you have a world of trouble.  Less severe that that is the hundreds if not thousands of dollars lost on furniture, shoes, televeision remotes, cameras, plants (which can be toxic) ... the list goes on and on.

You cannot correct or punish your dog after the fact.

Prevention

Confinement to a crate when you are away is not a punishment.  It is a way to ensure that your home and dog will be secure in your absence.  Leaving and untrustworthy dog loose in the house is setting your dog up for failure.  How will he/she know not to chew on items that are not his?  Be sure to leave a "safe" toy in the crate that he cannot swallow or choke on to keep him entertained while you are away.

Keep your dog or puppy on line in the house until he understands what is yours and what is his.  This will allow you to know where your dog is at all times and praise your dog for appropriate chewing.  If the dog begins to chew on something of yours, give him a verbal, "NAAH."  Immediately replace the item and redirect to his toy.  As soon as he takes his own toy, immediately praise him.

Purchase a large amount of toys.  Whenever your dog has the urge to chew, there should be a toy within reach.  If you purchase twenty toys, give your dog five.  Every week you can rotate the toys so the dog always has a "new" toy to play with.

Take your dog on plenty of outdoor walks.  Exercise is a way for your dog to expend energy in a healthy manner.  Exercise and walks are very important.

You must catch the dog in the act of chewing inappropriately for it to understand.  Do not assume it will immediately understand.  You must be consistent and persistent.

Introduce items that you do not want the dog to chew on.  Show him these items by holding them in front of him and tell him, "NAAH," or "LEAVE IT."  Do not mistakenly entice the dog.  If it makes contact with the items again, tell it again, but more sharply, "NAAH" or "LEAVE IT."  Immediately show the dog his own towys and in a soothing voice praise him.

Hold a toy while the dog chews on it.  This will teach the dog that you are in charge of the toy.  If it's teeth come near your skin, quietly tell the dog, "NAAHHH."  Praise him/her as it chews on the toy without thouching your skin.

This is a quiet exercise that will teach your dog waluable lessions.

Never roughhouse with your puppy allowing hm to chew or come in to contact with your skin.

You must praise your dog for stopping negative behavior instead of punishing it for doing negative behavior.  Remember, do not set your dog up for failure.