Dog Tricks -- Hang Dog
This trick is very easy!
Have your dog sitting or standing. You're facing him.
Watch for any downward movement of his head. As soon as his head moves down CLICK! and treat. You may have to do this a few times because your dog won't believe it's that easy. Then you can start selecting for lower head drooping. Soon your dog will be drooping his head and sitting there looking like a vulture. Keep clicking and treating. Add your command, "Hang Dog."
You can work on having your dog hold the position longer by delaying the click and treat, but be fair.