I encourage you to consider your own foundational inspirations when it comes to the written word. Who made you want to write in the first place? What works do you think are perfect — the ones you keep coming back to? Whose skill do you aspire to channel or match?
You can listen to your cast of characters at any stage in the writing process, but it might be especially useful near the end when most of the story is fleshed out. It can be a good check of your story logic and add a last ingenious layer of polish.
Self-publishing used to mean forgoing the resources of traditional publishing and running your entire independent enterprise by yourself. Thanks to technology and the increased connectedness allowed by the Internet, indie authors now have access to experts, marketplaces, and readers. What's not to like?
Authors want to manipulate readers' thoughts — this is why we read, after all. We love getting swept away into new worlds, with new people and ideas. Getting a reader's thought map is a great way to hone this skill.
Of course, not every self-published author is going to hit the bestseller list. But, you have a better chance if you apply some of the lessons taught by those who have.