Puppies start to lose their puppy teeth around four months of age. By seven months your puppy should have a full set of adult teeth. During this period of time the chances are good that your puppy will experience some discomfort and try to alleviate that pain by chewing on things. Chewing is a normal behavior for dogs. Instead of discouraging your puppy from chewing, redirect his chewing to appropriate items.
Puppies should not be allowed run of the house unsupervised. It is your responsibility to ensure that the items your puppy chews on are acceptable and to do that you need to be supervising your puppy in the house. If your puppy begins to chew on a piece of furniture or other inappropriate object, simply tell your puppy 'no' or use a verbal correction such as 'aah' and redirect your puppy by calling your puppy to you. You can then reward your puppy's correct behavior by giving your puppy something different to chew on. Praise your puppy for chewing on appropriate items.
The objects you choose should be safe for your puppy. Don't use plastic items which might be fragmented and swallowed and don't allow your puppy to chew on old shoes if you don't want him chewing on new shoes.
You want to have about three different chew items available for your puppy. This ensures that whenever your puppy has a craving to chew, something will be handy for him to chew on. Too many different items may lead your puppy to believe that everything is a potential chew toy which is just the opposite of what you are trying to teach.
While some dogs won't chew much at all after they stop teething, it is more common that young adolescent dogs go through a second phase of heavy chewing, usually around one to two months after they stop teething until about eighteen months. If you have already taught your puppy what is and isn't a chew toy, this period of chewing will be much easier to control as long as you have appropriate chew toys on hand to satisfy your dog's chewing habit.