I am a packrat too, mostly in way of papers. I keep thinking im gonna need my papers later to save my arse. I used to have paid phone bills that were 7 years old cause I kept thinking they were gonna come back at me for more money for some dumb reason. They were all paid of course, I jsut couldn't bring myself to get rid of them. I got a new system now.
Basically i only allow myself two file boxes for papers. One is for old files that I just absolutly must have and can NOT get rid of them for whatever reason. My oldest file in there is 13 years old.

Anyways that one is not allowed to spill over. If I can't shove anymore in there I have to find something in there that can be tossed in the garbage. The second file box is for current files in use only. Current bills, and current files that I need to access at all times. I am the type of person who when get on tty and having a discussion with one of my bill people that i need to be able to yank out the file right then and there and not go looking all over the papers for all pieces of paper related to that company. This was helpful for me.
Now for the other stuff, Junks and odds and ends.
Get a few of those big plastic totes with lids. No more than 3.
Go through your items and toss in these tubs what you feel you must keep. (get to the organization later) Just toss in there what you feel you must keep. Once those tubs are full and can't close then you know you are at your limit. Trhow the rest of the stuff away. If you come across something you must keep then you must displine yourself and take out one that is in the bins and exchange it for the other.
REst just pile up in the garbage and DONT DO NOT give second thought to that one items.
Once all done then You can go through your 3 tubs and sort them according to items for easy to find.
thi sis what I do and works well for me. Been doing this for about 5 years now and the clutter is less and less now.
the first itme was the hardest. I just had to grimance and throw a bunch of stuff away.
rule of thumb, if you haven't used it in over a year its a safe bet you can live without it.
Don't fall in the trap of saying to yourself, gosh I forgot all about this, I can use this still. That is how stuff gets piled up and then forgoten for anotehr year.
So stick to the rule of thumb.
BTW I only use two tubs now.