From an interview with Martin Gardner of The Whys of a Philosophical Scrivener "fame": "Martin Gardner: Yes, my files are my number one trade secret. It began in college with 3 by 5 file cards that I kept in ladies shoe boxes. I had a habit then (this was before copy machines) of destroying books by slicing out paragraphs and pasting them on cards. A friend once looked through my cards on American literature and was horrified to discover I had destroyed several rare first editions of books by Scott Fitzgerald.
When I began to earn some money I moved the cards into metal file cabinets, and started to preserve complete articles and large clippings and correspondence in manila folders. These folders are now in some twenty cabinets of four or five drawers each. And I have a large library of reference books that save me trips to the library. I have not yet worked up enough courage to go on line for fear I would waste too much time surfing the Internet."
He kept up with his "interests by taking scores of periodicals that deal with topics I may write about, especially science and math journals. (See The Mind at Play in the Skeptical Inquirer for more.)
I must say that I never cared very much for him as a philosopher. He always reminded me of the "modest expert" Robertson Davies emulated.