Write an Outline
Before you start writing your book, write an outline.
It doesn’t have to be detailed. It’s a roadmap, not a substitute for the book. No-one but you need ever see it.
As a rule, the outline lists the chapters that will make up the book, with the main argument of each chapter, the main takeaway you want the reader to learn, and suggestions of the arguments, examples, and stories the chapter will include.
It’s a great way to ensure that the structure of the book hangs together, that each chapter builds on what has done before, and that you’re not repeating or omitting information.
I’d never start writing a book without an outline. It sets your guardrails and keeps you on track.
But don't let it become a stick to beat yourself with.
I once started writing a book with two authors, one of whom was Chinese American. We planned the book with eight chapters because eight is lucky in Chinese numerology.
When we finished the first draft, it was clear it didn’t work. I had shoehorned the content into the wrong shape. A quick call gave me license to restructure the book from the top.
It was a pain to change things so late in the process … but it worked.
So write your outline before you start. And be prepared to throw it out at any time it becomes more of an obstacle than a help.