Goodreads has gotten a reputation for being tough on writers who want to share their work there. The Goodreads culture doesn't accept outright spamming or hack work, but writers who make an honest effort often find it to be the best word-of-mouth site online. Authors who are successful on Goodreads go in with a plan, and spend the time to use the site effectively for great marketing results.
Build Your Base
Goodreads is just another social media site at heart, and the best way to use any of them is to talk with people, not yell at them. Social media is all about conversations, and at Goodreads they're all about books. Sign up as a reader at least a month or two before you begin your serious promotions, just to build a base. Review books honestly, giving your opinions. Search reviews of books you like and send friend requests to people who share the same opinions. The idea is to build a base of acquaintances who share your literary taste, and will presumably like your book as a result.
Build Your Profile
Write your author profile and make it as interesting as possible, but include aspects that reflect similarities between it and your reader personality. You want it to be clear that you're the same person, not a fake persona trying to take advantage of readers for reviews. Add a picture and bio, keep adding to your favorite books list, keep reviewing other books and add to the discussions in the groups. Update your profile frequently to keep it interesting by adding videos, including blog posts, and sharing writing from other, similar authors.
Build Your Audience
Goodreads offers you multiple ways to get the word out about your books, but you have to be subtle about them. Any hint of pushiness will incur the wrath of snarky reviewers who, rightly, expect the site to be oriented toward readership and not salesmanship. Create a book giveaway contest and make it last the entire allowable 30 days. You'll need to have physical books for this option, but it will pay off. Everyone who enters the contest will have your book name on their dashboard, reminding them to check it out. Once your book becomes moderately well-known, create an "Ask the Author" group to answer questions and talk about your book or series. Continue to review books and join discussion groups.
Build Your Reputation
You've only got one chance to get it right on Goodreads, but you can reap huge rewards if you grow your fan base there. Never respond to negative reviews, it's always a losing battle. Always answer questions and emails. Discuss others' work much more than you do your own. Keep your contributions to 30 minutes a day or less. It's a valuable tool, but too much participation can start to look like desperation.