If you have ever taken a writing class or an English class, you have heard this question: who is your audience? Who are you writing for? It is crucial that you know this before you put your thoughts together — let alone start to write a book.
It is amazing how many books, articles, and presentations are written by people who clearly did not have the answer to this question. They wrote because they had something to say — without thinking much about who they were saying it to.
What needs does your audience have? What challenges is your reader facing? What language does your audience understand? How much patience will your reader muster to wade through your prose? What result will they have obtained upon completing your book?
Every reader is an individual. You may think of your books market has a crowd, but each reader is just one person. And if they are to buy your book, it must speak to them. They must see themselves in its title, its subtitle, its contents, its promises.
Create a persona that represents your reader. Design a fictitious character that embodies qualities of your audience. Then draw a picture of them, and write their characteristics on the picture. Keep that picture in view while you write. That way you will remember who your audience is.