As independent authors, we're all in it together. We learn from the mistakes and the success of other authors. We can share our stories (both books and personal) with each other. And just between you and me, it's wonderful to have people to complain to who understand your struggles.
When you help other authors, they help you to. When everyone helps promote each other, indie authors get more exposure. Most people think mainstream is the best or only option. People aren't always open-minded about reading self-published books. They don't always realize that the big, popular authors were once average, "hopeless dreamers" with nothing but a blank page and a full head. When all of us support each other, we open up people's minds to trying our books. Once they try them, they'll realize we're just as worthy of the "Author" title as traditionally published authors.
So, how do you help other authors?
Read other people's work.
Give honest (but kind!) feedback. If you don't like the book, don't publicly post a negative review. Instead, contact the author privately and make your suggestions.
If you did like their work, review it all over the place. Amazon. Goodreads. Your blog.
Like their author page, and tell them you're a fan. I promise you, it will make their whole day!
Promote the work you love. Share, share, share all over social media. Post their book links. Post your review. Post about what you're reading next.
Basically, any support you would like, give it to another author.
I think we can all agree that the world would be a better place if everyone read more books. There's really no competition. Supporting each other helps create a better world, where not only is your book on everyone’s reading list, everyone’s reading list gets longer and longer. Help out other authors, and everybody wins.