I made a list at the beginning of the summer of a bunch of things I wanted to do in the house, and I spent a couple of days prioritizing it. Some things had to be done before others - the garage had to be organized so I could make room for crap I cleaned out of the closets, for example, and I had to clear out a file cabinet drawer to make rom for MIL's important papers (she moved to a nursing home, and we got her stuff).
Having the list helped a LOT. I was able to look at things at different times of day and in different moods, and decide which things were most important to me. It's also nice to have a couple of smaller, visible things you can do right away, to get the ball rolling (like clean off the kitchen counter, or sort a pile of papers).
If you need to get storage boxes, have them ready in advance, so you don't waste time running around.
I agree about getting things OUT of the house right away, to the garage (if you have one), or the back seat of the car, for recycling, donating, or trash.
I also agree with the others to work on living areas instead of the basement - though perhaps it might be worth it for you (for the future) to at least organize the basement into areas - papers, clothes, memories - that yo can sort through in small chunks.
When I went through a bunch of papers this summer, I sat on the living room floor and tackled them while watching a movie. I would bring out one paper grocery bag full of stuff at a time, and sort into three piles: save, toss, shred. The save pile was TINY, and I felt fabulous with every bag that went to the trash! It was very satisfying, and I didn't need a lot of time or space to chip away at it.
Good luck, and update us when it's over!