Do have problems keeping things organized? There are some areas in my home that are always organized and then there are other areas that seem totally chaotic. I can find things when I need them but no one else can. Even if I try to tell them where to find something, it's a lost cause.
I have started a plan of action, however. When I come across something, by accident or on purpose, if I feel like I don't need it or want it anymore, I put it in a "yard sale" box or the garbage. If it's not worth trying to sell, in the garbage it goes. I am making progress doing this. Now I just need somewhere to store the "yard sale" box!!
I have a basement full of stuff that I could probably get rid of. I could sell some of it on ebay if I would just get down there and pull it out of the boxes and photograph it and set it up on ebay. That is the plan, it's just not to fruition yet. This task seems overwhelming to me. I guess if I approach it like the rest of the house, it won't be so daunting.
Unless you need to do something like this in a day or two, you can do a little at the time or work at it an hour or two at the time. Whatever you feel is manageable for you is the best way to approach something like this. I'm not a professional organizer but I have learned what to do and what not to do by what works for me and what doesn't.