If, and only if, you actually catch your dog chewing on something he shouldn't, interrupt the behavior with a loud noise and offer him an acceptable chew toy instead. (ddfl.org)
If you catch your dog chewing on something they shouldn't, interrupt the behavior with a loud noise. (humanesociety.org)
Interrupting the behavior helps break the habit and encourages the dog to try another strategy. (animals.howstuffworks.com)