Clear your desktop, and put back only what you use daily. Store everything else in drawers, on shelves, or in your supply closet. If you don't use something — those kitschy bulletin board push pins a client sent for Christmas — give it away to a co-worker who might be able to find a use for it.
Sort day-to-day papers into action files. Label them clearly: bills to pay, receipts to enter, papers to photocopy, data for reports, items to discuss with your boss, or papers to forward to another department. Store them upright in a stepped desktop organizer. Don't make a "miscellaneous" file — if the information isn't important enough to have its own label, it belongs either in another folder or in the trash.