Generally, my motto is "Why fight entropy?"
My living space has always been (and likely always will be) characterized by some degree of clutter. I'm not entirely disorganized-- I follow the "stacks" system of organization mentioned by others here. I *usually* know vaguely which stack of papers contains what I'm looking for, and try to keep the stacks to a manageable 4 or 5 distributed through 3 rooms. (Luckily, my home is small.) Occasionally, I'll attack a single pile of documents and file them, temporarily forestalling some of the pressure of impending chaos. My attempts at organization really amount to nothing more than stopgap measures.
The only rule is that nothing on the floor should be tripped over or otherwise seriously impede walking through a room.
Yet I cannot tolerate sheer "dirtyness". That is, I'm horrified to go into someone's house and see garbage on floors, old moldy glasses or mugs, half-eaten pizza crusts, and I'm talking where every solitary inch of space in the room is filled by some form of refuse mixed with papers, items, or whatnot. Basically, I just can't stand the thought of attracting cockroaches and or other pest species. Ugh.
I guess I vehemently draw the line where clutter becomes garbage.