I'm a writer, though not yet an author. There is an argument about who you should write for. Many people write for themselves, if you want a journal then write for yourself. If you want to sell books, write for your audience.
Write, just sit down and write if you want to write a book. Block out time if that works for you, or write when the urge hits you. You can plan your chapters, or write by the seat of your pants (my preferred method). Treat writing like a job, put in the hours and you will see the progress
Do not edit as you write, let it flow freely without critique. When you feel like you're done with your book, or several chapters, then go back and edit. Don't edit too much or too frequently, this can become a way to procrastinate. Let that baby grow and fly.
When you think your book is done, ask some friends or acquaintances to beta read your work. In my experience its better to get the opinions of strangers, family will mostly always love what you write because they love you and while this is a nice ego boost, it ain't sellin' books. I have beta read for authors from Craigslist ads, with the agreement to post an honest review on Amazon. I get the experience of critiquing, free books and writing reviews. Do this enough and you can build a network that will help you back.
Then make corrections based on beta reads, get an editor, you'll probably have to pay for this but it may be worth it. Decide how you will publish. With Amazon, self-publishing is easy. There is software there to load your book and format it for e-publishing and print books. Keep in mind you will have to pay to print publish. And I think it's also worth the cost to buy an ISBN, last time I checked it was around $100 to $250 depending on some options.
All this being said, if anyone wants a beta reader, or an editor let me know, send me a purple moosage and we can work something out.