Here are three strategies for writing a book. My favorite approach? I've used and like all three methods, but one might work better than the others, depending on the project.
Of course there's the traditional method of just writing a book with your derrière in a chair and your hands on the keyboard, for 120 hours or more. If you like to blog, you might prefer the second method: blog first, compile later. If you are in a hurry, you could try the third method: dictate it and get the whole story down in audio form, in about 10 percent the time it takes to write a draft the traditional way (but spend more time editing).
Take your pick or try all three, but most importantly, believe in yourself and never give up.