Writing a non-fiction book or ebook on a subject you know a lot about is a bit like tidying the house. There is a ton of stuff in there (the house, and your head) and the challenge is to spread it all out, sort the good from the bad, then neatly arrange the good in a logical and satisfying way.
Let's start with that first task – spreading it all out. From a writing perspective, that means collecting as much information as you can in one place. That way you can stand back and have a good look at what you've got.