I am such a pack-rat, and it's an effort to get rid of things. I wish I could be more buddist about it and not have any attachment to any objects.
There are a few things that might work:
Having someone else week through the stuff and throw 90% of it away. Sometimes I can't bring myself to throw away that pile of old magazines but if someone else does it and they're gone, then it's done. Anything that you're unsure of (eg. personal papers) can go into a box and be set on her desk to be sorted through later.
Having someone help me purge one corner of one room may inspire me to de-clutter. Seeing how nice it is to have a clean corner may energize me enough to over-ride my packrat habits. It also makes keeping the house clean so much easier.
Redirecting my hoarding tendencies can also work. If I sort my clutter and put 90% of it into bags/boxes for charity, then I have that sense of accomplishment. As long as I can remind myself someone can use the item more than I can, I am ok.
If I am being reminded about waste/scarcity, I remind myself it's a WASTE to keep things I never use. If someone in need can buy my item from a thrift store and enjoy it, that's a good thing; keeping it on a shelf to collect dust is a waste. It would be greedy of me to hoard.
Sometimes I have an item that was a gift, and there is a guilt factor in getting rid of it. I justify it by thinking about the nice item should be enjoyed. If I simply don't enjoy it, it really needs to go to someone who will appreciate it (charity, give away, whatever). If it's objects from someone who passed away, I keep one or two things which really remind me of them. The rest of the objects go on to be loved in someone else's home.
Here is a GREAT site/book on dealing with clutter:
FlyLady.net: Your personal online coach to help you gain control of your house and home