Also make sure your dog is well walked before you cage them and leave them.
It helps enormously if the dogs mind and energy are quiet before they're left for ANY length of time. It's natural for a dog to want some quiet time after having been walked, if you try caging an unwalked or excited dog then you'll just be caging that energy with them and it has nowhere to go other than to make alot of noise, scratching at the cage to try to get out or to chew whatever blankets you have left him with.
Simply walking a dog really does help with alot of issues.
(I'm not suggesting you don't walk your dog just explaining what I do)