I became a writer by accident, and have now published four books. So, I know what it’s like to have little writing experience, and to grow to write a lot.
I’ll start off by saying that most people have false beliefs about how a book gets written. I used to think that to write a book, you would just sit down and write a book straight through. This is probably why I hated writing until I was deep into my twenties!
The steps I recommend are designed to break down what can be a painful process into smaller, less-painful steps.

Step 1: Build a Tiny Writing Habit

The first thing you need to do is to build a habit of writing. Many people will tell you to build a habit of 1,000 words, but that’s just insane. You might meet that goal the first day, and maybe even the second, but then what happens? You oversleep your alarm clock a few minutes or you catch a cold, and you use that little thing as an excuse to not write today.
I interviewed Stanford professor and habits expert BJ Fogg on my podcast, and he told me about “tiny habits.” Basically, you should shoot for the smallest habit you can possibly imagine. That might be to write five words a day, fifty words a day, or even one hundred.
The point is that you pick a habit that is so small, you can’t possibly make an excuse not to write. It becomes harder for you to do the habit than it is to not do the habit.
If you keep writing every day, suddenly, you’ll be able to write much more, with less pain. Stick with the tiny habit, but if you write more than that target, that’s fine. Just don’t write less. Congratulate yourself just as much for writing fifty words as you do for writing 1,000 words.

Step 2: Learn About Books

Most of us take books for granted. We don’t think about how much thought and consideration goes into getting people to want to buy a book.
Make a habit of downloading free Kindle samples of books. Read a bunch of them. Think hard about why someone would want to buy the book based upon the title and subtitle. Read the Amazon reviews. Why did someone love the book – why did someone hate it? Even more valuable, why did someone almost love the book.
As you read Kindle samples, ask yourself if you’re personally compelled to keep reading as you get to the end of the book. The beginning of the book is really a part of the sales funnel, so pay close attention to it.

Step 3: Build a Publishing Habit
There are lots of emotional barriers to get over in writing, but also in putting your work out there. If you have a writing habit, you’re busting through those barriers for writing on a daily basis.
Now you need a publishing habit. Make a habit of publishing something every day. Again, you can start with a really tiny habit. I think a Medium is a good place, but you could even do here on Quora if you’re practicing for nonfiction on a topic.
As you publish, pay attention to the fears that you have each time you publish. You’ll probably publish many things where you feel embarrassed or afraid, only to find out nobody really cares. You’ll also publish things that you expect people to really love, only to find out the same.
I like Medium because you can see what people highlight, and the “clap” the feature also helps you see what resonates. This is all very valuable information because it helps you see in real-time what resonates.

Step 4: Build an Email List

If you’re going to go through the trouble of writing a book, you want someone to buy it. The best way to find buyers for your book is to already have fans.
Sure, you can build an audience on Twitter or Facebook or here on Quora, but you don’t really own a direct line to that audience. This is why you need an email list.
You can start with a simple sign-up at the end of each post you publish with your publishing habit: “Sign up to get updates from me »”
You can build up to giving bonuses for each sign-up, such as a short story or a list of tips.
ConvertKit (affiliate) is the best email provider for authors. I personally use ActiveCampaign (also an affiliate), which is a little more complicated.

Step 5: Write a Book Title That Will Sell

I cringe when I think back to the book title ideas I had for my first book ideas. Heck, I cringe when I think about some book title ideas that I have currently.
Coming up with a good title for your book is very important, and very difficult.
You want to balance having the right keywords with having something compelling or clever.
Keywords are important because people search for books on Amazon.
I admit that’s a ridiculously long title and subtitle combination, but I called it that for a reason: It’s jam-packed full of keywords that I know, through research, that people search for on Amazon. The book gets lots of organic sales!
You can also attract people to your book with a clever title. But it has to be a title that is: 
1) clever or cool-sounding, 
2) conveys what the book is about in some way, 
3) passes the “cocktail party test.”
Imagine you’re at a cocktail party, and you’re telling a friend about a book you’re reading. How does it feel to tell them you’re reading that book? Does it feel good? Does it make you look good?
This is why a book like Deep Work passes the cocktail party test. It feels good to tell someone the work you do is “deep.” If a book were called The Small Penis Owner’s Handbook, that would not pass the cocktail party test.

Step 6: Write an Outline for Your Book

We’re halfway through the process, and we’re only now writing an outline!? If I could blame one thing for why I hated writing as a kid, it would be the outline. Every damn English teacher I had made us write an outline before we wrote a paper.
Well how the hell are you supposed to know what you’re going to write about before you write it?!
Through your writing and publishing habit, you’ve started to develop a “universe” in your mind on a particular topic, or a series of topics (even if you’re writing fiction).
Now that you have some idea of what you want to write about, you can try to give structure to that writing.
I personally never have a completed outline that I stick to. I start to outline, and then if some prose comes to me on a particular bullet point, I start writing prose. The next day when I come back, I’ll start writing an outline all over again from scratch.
Force yourself to write an outline of your book. Accept that it’s imperfect, then move on.

Step 7: Write a First Draft of Your Book

Now that you have an outline, you can write the first draft of your book. Channel your writing habit into filling out that outline. Your tiny habit will have to get a bit bigger now.
Make a habit of writing 500 words a day, filling out that outline. I like a program called Scrivener for writing really organized projects, but use whatever you’re comfortable with.
Let yourself be sloppy here. Remember, it’s the first draft.

Step 8: Read the First Draft of Your Book

It’s an amazing feeling to print out your book at Office Depot and bring a stack of papers to a cafe. Sit down, shut off your mind, and try to react to your book like you’re someone who has never seen it before.
Don’t bother marking down spelling and grammar mistakes here. You’re trying to feel the book as a whole. If you think about details, it will distract you from that.

Step 9: Restructure Your Outline

Now that you’ve read the first draft of your book, you can restructure your outline. You may need some incubation time between reading your first draft (maybe a couple of times) and restructuring your outline.
Stephen King recommends to authors to not even read the first draft of their manuscripts until several weeks after finishing it. You really do need some time for your mind to make connections.
If you give yourself a few weeks before you restructure your outline (while still keeping a writing habit) when you revisit, something magical happens. Try to write a new outline from scratch. You’ll probably find your ideas are crisper than ever.

Step 10: Write Your Second Draft

Now that you’ve written the whole book, consumed it, and restructured it, you can rewrite everything, using that new structure as a guide. There may be lots of details you need to research.
Again, keep a habit, and stick with it. You’ll find parts of the second draft come very easily to you since you already have the first draft in your mind. Things will be crisper.

Step 11: Write Your Final Draft

Now, you can start worrying about things like sentence structure, grammar, and spelling. Print out your second draft, go over it with a red pen (I prefer green). Share it with friends or your fans. (I shared the second draft of one of my eBooks with my readers on Google Docs, and they crowd-edited it.) You may also want to hire an editor or proofreader.
Well, that’s how you write a book.

How to publish a book?

As far as how to publish a book, that part is easier, if you’re willing to self publish. People forget that you can publish a book almost as easily as you can publish a blog post.
If you really want to get a feel for how to publish a book, I recommend you go to KDP, and try to publish 500 words, on literally anything, under a made-up name. Your “book” will be available in the Kindle store within hours.
It’s incredibly valuable just to go through the process of publishing on Kindle, just to see how simple it is. In fact, you should publish your first “dummy” book today before you even start any of the steps I’ve laid out above. It will change the way you think about book publishing.