Never store information by how it’s going to be used. Always store it by subject because the ways you may use it can change over time and can’t always be predicted. And you should not have to know all possible future uses of information in order to store it in such a way that it can be found again when an unanticipated use arises. If necessary, you can index it by how you think you’re going to use it.
You should store information first by subject (astronomy, gardening, etc.) and second by type (theory, task, essay topic, etc).
Expand and subdivide, expand and subdivide. Storage structures, that is.
Capacity of various storage structures:
card-binder about 100 notes/ideas
card-file about 600 notes/ideas
page-binder about 1,000 notes/ideas
page-file about 6,000 notes/ideas