There are two basic techniques for how to write a book — or for that matter, any piece. They just become more defined in a book because of the length.
The first is: begin at the top left hand corner of page one and finish at the bottom right hand corner of the last page, and in between follow your nose. We’ll call this the ‘free-form’ method.
The second is: plan everything out. Design the structure of the book with chapter and sub-chapter headings, right to the lowest level. Then fill it up. This one we’ll call the ‘structured’ method.
Most writers to some extent use a combination of both approaches; and they are in any case suited to different types of writing. For example a psychological drama that explores characters’ reaction to their environment, really has to be free-form, to allow the characters to live and to actually respond in a convincing manner. I used this technique in The Warm Pink Jelly Express Train, a novel in which a straight man meets a transsexual and falls in love with her.