Puppies explore the world with their mouths. Puppies, also, play with things by chewing on them. When they are bored, they relieve it by chewing. Chewing is normal. It is natural. You cannot stop a puppy from chewing. That is the bad news.
The good news is that a puppy is more likely to chew on something that is new to him than he is to chew on something that has been around for several days. You can usually protect your possessions by giving your puppy a new toy every day. If you purchase a new toy for your puppy every day, you will soon go bankrupt. But most of us bring home free dog toys on a regular basis. And most of us throw them away.
Most things that we buy at the supermarket come in plastic containers of one kind or another. There are gallon milk jugs, two liter Pepsi bottles, I Can’t Believe It Is Not Butter tubs, as well as detergent and laundry bleach bottles. All of these can be recycled as dog toys. So can plastic flower pots from the nursery. Practically any plastic container that you bring home can be put to good use protecting the other things that you own.
If you can remember back when you were a child, it did not matter how many Christmas presents the jolly old elf brought, by the New Year, you had nothing to play with. “But Momma, this stuff is sooooo old.” Dogs are, in many ways, just like kids. New is exciting. Old is not. Your puppy will play with a “new” jug. After it has lain around for a day or two, he will go back to chewing at random. To keep your dog from chewing things that you do not want him to chew, you need to keep him supplied with a new toy. If you think that the toy that thrills him so today will work tomorrow, you are mistaken. Give him a new toy every day.
Some puppies, despite having a new toy, will continue to chew on other things. Usually this obsessive chew spot will be one specific place. When this is the case, you must, somehow, make the preferred chew spot distasteful.
If his favorite chew place has a hard surface - such as the rung on a kitchen chair - there are a number of different ways to make it an unpleasant experience. You can purchase a product called “Bitter Apple.” This deters most puppies. Some, it does not slow down. Tabasco Sauce or another super hot pepper sauce painted on the surface works for many puppies. If neither “Bitter Apple” nor a hot sauce stops him, ask your pharmacist for Quinine in solution. Quinine is one of the most bitter products available.
If his chew spot is a rug or carpet or a throw pillow, get some pickling alum (used for making pickles crisp) from the super market or just ask your pharmacist for a box of alum. Alum is very astringent. Getting it in your mouth gives the same sensation as biting into a green persimmon. It is unpleasant. Sprinkle the alum liberally on the chew spot. Later, after your puppy is convinced that he doesn't’ want to chew there any more, you can vacuum the alum up.
When you catch your puppy in the act of chewing on something that you do not want him to chew on, reprimand him. A moderate slap on his butt is not inappropriate. Stop him from chewing. Then give him an object to play with that you approve of.
When you cannot supervise your puppy, he should be safely confined. You can only change a behavior while the behavior is happening. You have no control over what he does when you are not with him. Allowing him to misbehave because you are not supervising him undoes what you have tried to teach him.