Creating and enforcing a clear-desk policy

I can never claim to be a tidy person, just ask my wife, but I do have a rule that I clear my desk at the end of every day. Client documents are shredded or filed in a cabinet, and the keys, along with backup tapes and other media, are put into my fireproof safe. It doesn't take long and is a worthwhile task; I know confidential data is safely stored, and I know where it is -- both key tenets of good security. Implementing a similar policy in business should be a standard practice.