I've not said "no" so much in my life as I did about 20 minutes ago. Gatsby discovered that he really dug this area between my chair and my couch, an area which houses my magazine rack and about six cords to various electronic apparati (computer, lamps, etc.). He decided that chewing on power cords was a good use of his time.
I "no"-ed him and yanked him out by his collar (gently, obviously) and said no, no, no, over and over again. If he opened his mouth, I said no. If he moved toward a cord, I said no. Eventually we got to the place where he had his nose one inch from a cord and would lean in towards it, watching me, and when I said no he'd pull away. Then he'd move back in. I'd say no. I believe this is known as "testing."
We both passed. Gatsby stopped and laid down next to the magazine rack without chewing on anything and gazed up at me with hurt eyes. I told him he was a good dog in my "yay" tone of voice, and he eventually crawled out and sat in my lap and licked my nose.
He's now passed out on the ottoman, exhausted, and I'm not far behind.