When you're writing a book (actually, a series of books) with a bunch of plot lines, you need a way to keep track of what's going on. How can you structure the book so that everything fits, and moves, and you don't leave out any of those zillions of characters and subplots? How do you figure out what goes in each chapter? Well, apparently J.K. Rowling made a spreadsheet -- the old-school way, using a piece of paper. (Yes, prior to computer spreadsheets, a "spreadsheet" was done on paper.).
One sample sheet popped up on the blog état omnipotent in 2010, though apparently this page had been floating around for years (I've read some comments suggesting that Rowling herself released it on her website for fans). Anyway, état omnipotent's author wrote:
A spreadsheet plot written out by J.K. Rowling. Her approach to spreadsheet plotting is to divide the columns by chapter number, story timeline, chapter title, main plots and subplots.
Note the organization by month, as well as the clear distinction between the main plot, the primary subplot (labeled "PROPHECY"), and five other subplots -- they're all a bit sketchy, and often aren't mentioned in the book's text, even though they're still occurring in the world of the book over time.
This one is from Order of the Phoenix, although it's just one page and it's an early version (you'll note "Elvira Umbridge" mentioned rather than Dolores; Grawp is apparently a cousin at this stage; and the D.A. and the Order of the Phoenix appear to have swapped names). My favorite notes are "gory here" spanning chapters 22 & 23 related to the D.A. (actually the Order as it appears in the final book), as well as the treatment of chapter 19, which has the placeholder title "(Xmas)," no main plot development, three totally blank subplots, and a subplot including "big reunion" circled. I guess even plots take a break sometimes.