1) Shove everything that isn't where it belongs into a room/closet/cupboard. Dust lightly outside of said room/closet/cupboard. Smile a lot.
2) Make piles. Make piles and piles and piles. As long as things are in piles, the room is clean. Believe that. Fully.
3) Pull EVERYTHING (and I do mean everything) that isn't exactly where it's supposed to be out and dump it in the middle of the floor. Start putting things back exactly where they're supposed to be. When I was a child--and yes, this was my method back then, too, and it drove my mother up a wall--this took me anywhere from two days to a week to accomplish, depending on if I was doing my closet or my whole bedroom. Now it takes a week to two months, depending on if I'm doing my closet or my office.
Guess what I did Sunday night?
The pile is growing in the center of the office.... I haven't done this in far too long, as I have hovered between method 1 and a traditionalist mode where I put things away for nearly relevant values of "away." (Books on bookcases, for example, just not in any order that I can actually enjoy, or, you know, find things on. This got out of hand when I moved a bookcase into a closet in close proximity with a dresser and can't actually, you know, access the bookcase the way god intended. Guess where the dresser is going in the next few weeks? I'm DONE with this. Completely done.)
Further, I have thoroughly determined I do not need such precious items as:
-a pair of red suspenders from that Halloween where I dressed up as Pokemon trainer Misty
-a juliet cap I made for my first Renn fest costume
-developing tongs for photography, new, in the package
-Strawberry Shortcake dolls from my childhood
-puzzles I've completed
-43 jillion sewing patterns, considering I don't actually sew, not really
Ultimately, I will keep the keepsakes that actually mean something--not dolls that smell like lipgloss--and I think I'll keep my drawing implements, too, on the off chance that I might take that up again someday... but for the most part, I'm going to spend the next month downsizing.
Who knows. Once I can actually see my reference bookshelf again, I might go so far as to even cull it. Crazy thought, that.