Step1
Write, write, and write some more. One cannot make a novel if one does not write. Write something every day. Keep a journal. Write a few sentences. Write about an interesting plant or something that happened at work. It doesn't matter what you write, just write.
Step2
Learn new things. Don't be afraid to ask a myriad of questions. Be curious about everything and everyone. It is said that authors must write what they know. If an author knows little to nothing about its subject, there is little to nothing he or she can write.
Step3
(Optional. Those writing nonfiction can use this step as well, but it is optional.)
Take a scenario you are in or have been in and think of a different outcome. Imagine what would happen in an alternate world.
Write down dreams you had the night before. Find ways to characterize people in your life into your story.
Try to describe everyday things in different ways.
Step4
Get to know your subject. If you are writing a nonfiction book, do as much research as you can, then do more. By the time you are done with the research, you should be an expert on it, or don't write about it. If you are writing fiction, know the world your characters are in and know your characters better than you know yourself. Understand what makes them tick and why.
Step5
Use a sounding board. If you get stuck, talk the story out with somebody. There are reasons a person gets stuck, and usually it is because something is not making sense or something is not right in the writing. Talk it out, see where it goes.
Step6
Write, rewrite, write some more.
Is there a theme here? Write your story until your story is finished, make sure you have done all that is possible for you, then send it to an editor.