Chewing on furniture is a typical behavior for puppies that can also be a very expensive habit that must be stopped as soon as possible. The primary reason for dogs to chew is anxiety and boredom. A dog that is left alone finds chewing a great pastime and anxiety reliever while causing the owners anxiety! Limiting your dogs access to your furniture while you are away or out of the house is step number one in preventing harm to your belongings.
If you do catch your dog chewing, be stern and reprimand him. Make sure he is aware that you are not happy with him. As with all discipline, be consistent and firm. A good way to make sure your dog realizes that even when alone and bored, he should not chew is to watch him from another room. Watch him when he is under the impression he is alone and as soon as he starts, immediately come in and reprimand him.
If you are losing patience and not getting anywhere, you might want to go to your local pet store and get an anti-chew salve, spray or cream for the furniture. Talk to the pet store owner and he may recommend one item over another.
The other approach to the problem is to help allevaite the boredom your dog is experiencing. Leave a TV or radio on, any type of stimulation. If possible, leave toys around, especially of the chewing variety.