You should check out the Bruce Sterling speech from Reboot11. He talks about categorizing everything you own into four categories: beautiful stuff, stuff that you have a strong emotional connection to, tools that are absolutely needed to live a better life and "the rest".
Everything in "the rest" category you should get rid of. Video of speech is here:
http://video.reboot.dk/video/486788/bruce-sterling-reboot-11
"Murder your darlings" actually means something more specific than that. It doesn't just mean not to be attached to passages you like, but to be especially suspicious of them.
Maybe it's just me, but I can't relate to a feeling of "guilt" simply because I haven't used something in a while. I'm not attached to my stuff, I just don't care as long as the place doesn't look cluttered.
The only reason I have to toss stuff (that's paid for) is if it takes up too much space. And I have acres of storage room.
My favorite method of getting rid of possesions is just sell the 10% you use the least. Then repeat on the remaining stuff. The first iteration is pretty easy. Once you actually experience how little you miss the items the 2nd, 3rd, 4th etc iterations come naturally.
The pursuit of happiness (Mark Pilgrim)
1. Stop buying stuff you don’t need
2. Pay off all your credit cards
3. Get rid of all the stuff that doesn’t fit in your house/apartment (storage lockers, etc.)
4. Get rid of all the stuff that doesn’t fit on the first floor of your house (attic, garage, etc.)
5. Get rid of all the stuff that doesn’t fit in one room of your house
6. Get rid of all the stuff that doesn’t fit in a suitcase
7. Get rid of all the stuff that doesn’t fit in a backpack
8. Get rid of the backpack