This article isn't like others you may have read about author social media and SEO (search engine optimization). Unlike those, I'm going to tell you exactly what you need to do to help get your message out.
Pick a good name -- one that uniquely identifies you and your work, and more importantly, one you can live with. Reputations aren't made overnight, and you'll be working under this name for a long time.
Get Set Up
First things first: start a blog. You need one. Not only will it help keep your writing sharp, it is also a tool for getting your message across. I can't stress this enough: your blog is your message. Social media is how you get that message out. Post frequently and regularly. You want to garner a following, but that's not all -- you want interaction too. Be sure to respond to your audience's blog comments promptly and thoughtfully. After all, no one likes to be ignored.
Limiting yourself to one or two social media accounts is like using a wheelbarrow when you've got a big rig truck parked in your front lawn. Do not limit yourself to just a few social media outlets. Open accounts with Twitter, Goodreads, and LinkedIn. Then open Facebook and Google+ accounts, and make pages on both. The aim is to make it easy for your audience to find you. Your readers might have Facebook but not Twitter accounts, or LinkedIn and Goodreads but not Google+, and so on. Don't have them chase you down, because in many cases they won't. You need to go to them.
For each of your social media accounts, assign the same brand-name you devised earlier in this exercise. Your goal here is to have consistency across all accounts so that your readers can find you on several outlets.
Get The Word Out
You don't have to post to each account individually, as that would cut into your writing time. Remember, you are an author first, and a social media wizard second. Writing is the end in itself. Social media is a tool for successful writing.
First, sign up for Buffer. It's a free social media integration app that will save you loads of time. Make an account with Buffer and link your social media profiles to it. All social media posts you draft in Buffer will be disseminated to all your accounts at once. Alternatively, you can schedule your posts for a future time.
Next step: syndicate your blog. This means setting up your other accounts to update every time you post a new blog entry. Sites like Goodreads and others allow you to syndicate your blog. When you syndicate, each time you post to your blog, the message can reach several outlets in the time it takes you to post to one.
Remember: The Dog Wags The Tail...
Writing is a conversation. Your words speak to your readers, and your readers respond. Don't speak to an empty room. Get out there and be heard.
Best of luck, and happy writing!