Using social media to promote your books is key in today's book marketing world. Here are some underutilized ways to increase your following:
Facebook - When other authors or acquaintances friend my personal Facebook page, I invite them to like my author page. You'd be surprised at the number of followers you gain.
Post frequently to your author page. And make sure that most of your posts are not "buy my book."
Link your author page to your Twitter account. I picked up some tweeters when I did that.
Instagram - Use hashtags (lots of them) with your posts. Thanks, Meagan Cain for the tip. My likes and follows increased as soon as I started the practice.
Post pictures and videos frequently. When I posted once a week, I didn't get much love or attention. The more I post; the more my activity increases.
Twitter - When people comment on my tweets or retweet, I usually follow them.
If you're looking to increase your followers, find people who have similar interests. Look at who they follow and who follows them. Follow their followers.
Use hashtags (usually no more than two or three). People with similar interests can better find your posts.
Other Ideas - Put your Facebook, Twitter, Instagram, blog, website, etc. in your email signature as links. Make it easy for people to find you.
Make sure to put all of your social media links on your website, Amazon AuthorCentral, and Goodreads sites.
And don't forget the social part. Make sure that you're interacting with others' content on these sites. Happy posting.