Have you ever been doing research for one project you are writing and run across something you need for a different story? That happens to me all the time.
In my office, I have a file cabinet on wheels. It's crammed full of info for all my projects and then some. I keep anything I find that I might someday need. To you that may sound like a mess, but I assure you it's not. I have organized it into file folders. I'm not sayhing that I have organized the file folders, because I haven't. I'm just saying that each topic is in a file folder.
Often times, the information I need most I find in the strangest places. They are where I never would have thought to look. It's the accidental findings that I value most. If I don't print a copy of it now, I'll never find it again. That is the reason my file cabinet is so full. I can't let any treasure slip through my fingers.
I'll bet you are wondering if I ever use these things in my file folders. I do. These files actually help me when I'm searching for something new to write. When I have used the folder beyond what I need it for, I shove it into a drawer in another file dabinet. That way I have room for more research, and it's nearby so I can find it if the need arises.
To me, part of writing, is the research. I love it, and the amazing treasures I find. Every day to me, is a new adventure.