Andy Weir is best known for self-publishing The Martian, until it was picked up by Penguin Random House. It quickly transformed into a bestselling novel and made into a future length movie. In a recent interview he gave some useful advice to anyone thinking of being an indie author.
First, you have to actually write. It’s easy to imagine a story and think about plot points. But until you’re putting words down on paper, you’re just daydreaming. When you start physically writing, you start realizing problems with your story. You might have been thinking of this awesome backstory, but that’s going to take 40 pages to describe, and that might be boring. So once you start writing, you’ll find the problems.
Second, resist all urges to tell your friends and family your story or ideas. The reason is that most writers — I am, certainly — are motivated by a desire to have an audience. You want to have other people read your story and experience the things that came out of your imagination. But if you tell them your story before you write it, that satisfies your need for an audience. And you might not put it to paper just yet. Make yourself a rule: that the only way people will experience your story is by reading it.
Finally, there is no better time in history to self-publish. It can cost you literally nothing, if you use services like Amazon or Barnes & Noble. There’s no old-boy network between you and your readers. It can be a pure meritocracy. The only risk you’re taking is the time you spend on the book. But theoretically, you wanted to spend that time anyway, because you love writing.