Searching Google will get you the answer but here are a few tips to start. The dream is to write a book and sell millions of copies. Nice but not likely. Niche

Searching Google will get you the answer but here are a few tips to start. The dream is to write a book and sell millions of copies. Nice but not likely. Niche is nice but it's hard to figure out which is profitable. Write the book for the joy of the project don't expect to be inundated with cash or get any cash for that matter. Even if you can get a book contract from a publisher, they take most of the cash and you see some money only once all the expenses are covered. If the subject is additive for your career and expertise then do it with out question. It's always good when you can bring it up to add to your credibility. Set the tone of the book. Who is your ideal reader? Research your audience they will tell you what they need. If you're the expert and you're teaching novices then make sure you don't write above what they understand. The book's goal is to teach not have to buy another book to understand what you just told them. Experts are usually bad teachers. As an expert you forget the basics that got you to understand what you know. You'll need to get someone else to tell you what's not understandable. Create an outline, and refined it with your potential reader helping you. Once you have the outline start writing. You'll want to write a few thousand pages. Write whatever comes to mind. The outline will help you. What you want is to have enough to edit it to a point that's clear enough to teach and you'll need to cut it down to a few hundred pages. It's easier to have independent editing and writing sessions. Avoid doing both at the same time. Your writing will be more difficult and take longer. You'll have to be your own editor. Once you have a finished manuscript. You can get the technical procedure on how to convert it to the different book formats by using Google. Also you'll need to learn how to promote it. Good luck with that, that's a whole other rat hole. I would get it to a point where you have a printed copy. You can give copies away and have a copy to look at yourself. It will be something you'll be proud to display. Lastly, don't use a word processor until you think you have a final copy. You'll waste so much time fiddling with the different word processor's options that it's just not worth it. Text editors are your friend.