I've been working on the decluttering for a few months now. I pick an item up and say, "Do I need this?" I have read "need" being determined by the fire test: If your house was on fire, and you had 5 minutes to save what you could, those are the things most valuable to you. The rest is crap and you can get rid of it. For me, though, after getting the dogs and cat out, I'd grab the stuff that's the most tedious to replace. My purse containing driver's license, insurance cards, glasses, cell phone, etc... and the folder holding my birth certificate, Social Security card, and title to my car. I've been stashing digital stuff on the internet (Google Docs, Picasa Web, and an online file storage service), but I'd probably still take my netbook. Next up would be my prescriptions, and a change of clothes. Tax documents if there's still time remaining.
I tend to keep stuff "just in case" I'll need it some day. Mostly, that some day never comes. I've recently thrown out a whole bunch of old computer component boxes, clothes I never wear, old papers and bills, magazines and catalogs, and plain old "junk." I've also sold a whole bunch of stuff via craigslist, and have a few things that will eventually go on e-bay. Old dog and cat collars and things get donated to rescue groups.
The other half of decluttering is organizing the stuff I'm keeping. I replaced my glass desk with a wooden one with five drawers. I bought a nightstand with three drawers. I got all my spare computer cables into a big plastic bin with a lid. All the manuals for the heat pump, appliances, and other house stuff are in the same cabinet instead of all over the house. The linen closet is even neatly organized now.
I know that sounds like a lot,but I have a long way to go in simplifying. I still have too many clothes, and a few pairs too many shoes. I don't really need 6 cat-5 cables or 4 co-ax cables or 3 s-video cables... I don't need 8 ice cube trays (they came with the house), or 4 phone books, or hundreds of DVD's. When I finish scanning in all my old photos, I can get rid of the printer/scanner. And the printer stand. The list goes on.
I try to tackle just one room or closet or drawer every week. I'm ignoring the garage for now, but its day will come. Every armload of stuff I get rid of gives me a greater sense of freedom.