You are your brand. Your author presence on social media should have a strategy, plan, and purpose. You want a unified look.
Drive Traffic to Your Blog or Website - One of your primary goals should be to drive traffic to your blog or website. Tweet links of your blog posts (new and recycled). Schedule them with a tool like TweetDeck or Hootsuite to post during hours you don't normally tweet. I schedule tweets at night or while I'm at work, and I've picked up new readers from different time zones. Schedule sparingly though. If someone follows you on different sites or views lists, you don't want hourly tweets of the same thing.
Analyze Your Content - Look at your posts and tweets. Are you getting likes, favorites, retweets, and shares? If not, consider rewriting your content. Make sure that you include videos or pictures. Also use hashtags (no more than two) to get noticed by like-minded readers.
Diversity is Key - Make sure your social media use focuses on the "social" part. You should join conversations, share others' materials, and thank those who share your stuff. People tend toignore you if all your posts are "buy my book." If you use hashtags regularly, make sure that you share others' postings from that list. You don't want to be a lurker.
Use Analytics - Facebook, Google, your website, and other sites have analytics. There is a lot of good information there about who's coming to your site and when. If you notice you have higher traffic on certain days, plan your posts then. Likes, shares, and retweets expand your reach.
Learn What Your Readers Use - Use the social media sites that your readers frequent. I learned this from Rachel Thompson of Bad Redhead Media. Google social media demographics. There is a lot of free information out there. Target your social media platform to what works for your audience. (The majority of Facebook users are women over forty.)
Be Adventurous - Be willing to try new social media sites and techniques. Try it and check your analytics. If it doesn't give you the results you want, modify it or try something else.
Look carefully at all of your social media sites. The colors, look, and writing style should be the same or similar. Themes are good. Your pictures and name should be the same on all sites. Make sure that you cross-pollinate your sites. List your website and blog in all of your biographies. Make sure that all of your links work.
I never knew how much marketing was involved with writing books. Best wishes for your writing and promotional projects!