We've had clutter problems off and on. Right now the cluttered spot is actually our shed, which has everything from extra couches and beds to three medium-sized moving boxes of just-junk-we-didn't-know-what-to-do-with after we moved.
What I found helpful when faced with the daunting task of cleaning out the MIL clutterpartment (from the other thread I started on this board) was to have three bags, one for trash, one for charity, and one for giving back to MIL or to friends. In one session I'd fill all three bags, and take the trash immediately to the trash, put the charity and MIL bags in the trunk (labelled) and then that would be it for that day. If I was feeling ambitious the bags were yard-trash sized, if I was feeling lazy they were grocery bags. I didn't do this every day, not at all.
The idea is to give yourself a stopping point that is NOT DONE. This was a problem for DH because he was used to the "do it until it's done" mindset, which is plenty useful sometimes but when dealing with a task that you simply CANNOT complete all in one fell swoop, it keeps you from ever starting. The idea that he was done when he'd sorted just ONE set of bags (and a lot of this stuff was from his childhood, so it fell on him to sort it) was very helpful.
We took a lot of pictures. Of ourselves in things MIL had saved, of DH's old science projects, of all kinds of things. They remind us quite as well as the actual object, because for many things, the memories that they bring back are important far beyond the importance of the actual object. We then happily tossed them in the trash or in the charity bag, knowing that if DH wanted to remember them, they would be there on the computer.
We tend to accumulate CRAP, as I think everyone does, and I think that this is where-other-threads-come-from. We live in such a tiny space right now that I have to CONSTANTLY look around and thing "do I need this? use it? how often?" about anything that might get in my way. We were, for a while, unable to use our couches, stepping around piles, etc. It has been tamed to a large extent, but only about a month ago could I finally say that I had a place for everything that I owned. And then we went to a garage sale and there's a lava lamp sitting on the kitchen counter that I have absolutely no spot for
. It really IS neverending!