Divide the house either front and back or left and right and clean half the closets.  Pulling everything out of a closet will not only help keep things from piling up over the years, it will also help give you a chance to preform an inspection of the walls, floors and ceiling in the closet.  Leaks frequently go undetected for a long time because the leak occurred in the back of a cluttered closet and no one knew.  It is a good idea to decide how frequently something should be used before it is just taking up space.  Is it three months, six months, a year?  This will help you make decisions about what to throw out and what to keep.  We only recommend doing half the closets in a month because it is a big job.  Half is enough.