I like containers (plastic, not cardboard...silverfish ick). Not only do they keep things organized, but they are a physical limititation to how much of each type of item you can keep.
1) Determine the size of container/s for each category of item (tools, books, stored clothes, mementos, etc)
2) Create 3 large spots in a bare area (definitely keep, not sure, donate, ). I like to mark off the 3 spots with painter's tape
3) Set out your boxes/containers, with tape and marker for labeling; try to keep like with like (ex: cords/electronics, tools, mementos, photos, office supplies, crafts/gift wrapping)
4) Indiscriminately haul out everything you own, in chunks; bring a box of heavy duty garbage bags for obvious trash to go right into
5) When a section fills the tape border, empty it appropriately (if keeping, place in designated container; if donating, physically put it in your car and drive it to donation spot; if unsure, you don't have to make a decision on everything yet, but try to make space in the section by seeing if there is anything you are ok placing in the other 2 piles. I find that after at least one round of filling the sections and placing things in boxes, and donating...it re-calibrates my expectations and the fate of those items in the "unsure" section become a little more clear.
* I like to do paper separately, since it takes so much time. Once a year or so, I'll touch every paper I own (except for mementos and medical records), throwing out what's no longer valid or needed. I keep them in labeled folders (warranties, receipts, taxes, financial, car stuff, house stuff, pet stuff, misc) and will go through a couple of folders per day until I get through them all. I also only do electronic billing when possible.
This works for me and ensures I don't get rid of too many things I'll regret. I have a couple boxes of mementos that I literally want to keep just so I can look at them every few years. Perhaps that's silly, but since I've restrained them to a certain amount of boxes, they're not hurting anything. It can be a fun an therapeutic process. I usually bring out wine and music/netflix too.
I also like this method because it allows you to lay things out long-term, without it melding back into the rest of the house (as long as you keep them in their taped borders). And you can do as little or as much as you'd like in a day.