The Harry Potter series was pretty intricate in terms of plot and character development for a young adult series, and that means J.K. Rowling spent a lot of time preparing to write the story to make sure everything lines up properly.
In order to help her speed this process up a bit Rowling created a plot spreadsheet to help her keep the story on track:
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.
The Harry Potter spreadsheet first made the rounds about six years ago, but since it's such a fascinating look at the process involved in writing the iconic series I figured it would still make for an interesting read...that is, if you can read really scribbly handwriting.
-Via mental_floss