Positive reinforcement is always best when training a dog. If your dog is chewing on your furniture, try distracting it by replacing what it is chewing on with a toy or acceptable item to gnaw instead. Praise it when it chews what it should. If you need additional motivation for your dog, try using bitter sprays designed to deter chewing behaviors in pets or put temporary barricades around furniture you don't want your dog to get its teeth on.