This is a note from C. Wright Mills about the importance of keeping a file:
[K]eep a journal. Many creative writers keep journals; the sociologist’s need for systematic reflection demands it. In such a file as I am going to describe, there is joined personal experience and professional activities, studies under way and studies planned. In this file, you, as an intellectual craftsman, will try to get together what you are doing intellectually and what you are experiencing as a person. Here you will not be afraid to use your experience and relate it directly to various work in progress. By serving as a check on repititious work, your file also enables you to conserve your energy. It also encourages you to capture `fringe-thoughts’: various ideas which may be byproducts of everyday life, snatches of conversation overheard on the street, or, for that matter, dreams. Once noted, these may lead to more systematic thinking, as well as lend intellectual relevance to more directed experience.