Have you ever noticed how you can instantly recognize a Stephen King or James Patterson book just by glancing at the cover? That's because they, and many other bestselling authors, are masters at branding. Everything connected to them -- their book covers, their website, and even their email signature -- are done in the same style, to create one consistent, recognizable brand. This brand recognition is one of the best pieces of free book marketing you can do, and it works best when you begin the process before you publish your first book. Creating a recognizable presence where readers see you can give you a significant boost in sales right from the start, but it only works if you plan ahead and stick with your plan. 
Visual Impact
Your brand style begins with the feel of your books, and grows from there. Do you write historical romance, military sci fi, or cozy mysteries? Check the top 100 books in each genre, and you'll notice trends in each niche. Certain colors, photo types and even fonts evoke the feeling of different book genres, and you'd be wise to follow along with the crowd for most of your branding style. You can add a little bit of your own flavor, but flowing cursive script is never going to give your readers the feeling of a space opera.
Find a style that fits with your book genre as well as with your personal taste. Pick fonts, colors, and even a style of photograph that will work for all of your book covers. From now on, every time you create something as an author, use these visual cues to tie it together with everything else you've done.
Social Media
Readers will become loyal fans if they have a personal stake in your success, and the best way to do that is to give them the feeling that they know you. Create a Facebook account in your author name and begin to chat with readers of authors in your genre. Don't push your career, just join in as a genuine fan of the niche. If you write thrillers, you must like them and read a lot of them, so it should be easy to hold conversations on the topics. Allow people to get to know the real you, and let them discover your writing career naturally. By the time you've got your first book published, you should have dozens or hundreds of people online who know you as a true fan of the genre, and they'll want to help you along because they knew you at the beginning of your career.
Once you have a good following on Facebook, move on to another social media setting like Instagram or Pinterest. Build one account at a time so you don't overwhelm yourself with marketing work, but post on that account every day to build your following as fast as possible. Use your branding on all your profiles, and post about your genre topics 80 percent of the time. The rest of the posts should be general topics, non-controversial, and designed to be popular enough to be shared as much as possible. The idea is to get your name around everywhere you can, however you can. The more places you show up as a familiar figure, the more ready fans you'll have when you finally publish your books.
Keep the Faith and May the Force be with You!
