(I don’t actually know anything. This is a rant of sorts, you probably shouldn't read it.)
I love my story, ok? That’s why I’ve spent hours writing, days imagining, and months thinking. That’s what makes a book; that’s how you do it. Classes and workshops and seminars on ‘How to write a book’ are clearly taking the long-winded approach.
You can’t teach someone how to write a book. The only way to learn is to write one. Yes, it will probably be terrible. The story, hopefully, will be great. But the writing? You’ll read back over your first draft and laugh at yourself, I guarantee it. Let it out though; laughing is good. You will also cringe. At this point the ability to highlight and cut should be taken full advantage of. Words shouldn't be seen as precious things. When in doubt, make a new file and store all your cut paragraphs in there. If you really think some arrangement of words is golden, mark it. Mining for gold is not fun.
Now I’m not bashing courses and the likes. They might name a course ‘how to write a novel’, but that’s just to get people in the door. They won’t tell you how to write a book, or where to find an idea. No, they’ll tell you about writing; the ins and outs, the ups and downs, and, with any luck, where to put an apostrophe. Count yourself blessed if this is done in an inspiring way. If you learn a lot of new things; congratulations you're in the right place.
(You should consider reading a book or a hundred as well as sitting in class. You CAN read a book and write your book at the same time. The stories don't get intertwined, and your ideas remain yours.)
Then they’ll make you write. You will panic. If you didn’t have an idea growing beforehand (in which case you should definitely write it down, but you might learn that fact later in the course) then your mind is going to go blanker than a big whitewashed wall. Whatever you come up with will be shit. If offered to read yours out loud, don’t. Don't make eye contact with the teacher just in case. If you feel in danger, think about crackers and jam to give yourself a faraway look and maybe, just maybe, the teacher will think you are presiding over a world you’ve created and leave you alone.
After that the rules come along. Rules rules rules. Follow them or watch your writing ambitions swirl down the loo. Or don’t follow them, if you have a good reason not to; it’s not that big a deal.
In a seashell
How do you write a book? Get an idea, love it, write it.
I can see the next question...
How do you get an idea? Ahem, well let me tell you. You just fricking get an idea, ok? If you need to ask how then I’m sorry but it’s never going to happen. Actually I’m not sorry. Your mind needs to be alive to get an idea. You clearly killed yours. Tut tut.
How do you complete a book? Write until you reach the end. Huzzah!
It’s still a bit shit though. Go to a workshop. With a book, or something book-like, completed. That way you’ll understand a lot more of what the host is talking about.