The content you post in these social media sites should be of high quality and compel viewers to read it. The most important factors are to have proper grammar, a relevant image and a link to a page on your website that is maybe the next part of your post. Otherwise you can always use social exchange sites in order to build back links like AddMeFast, however it shouldn't be a long-term plan to do so. If you use that too much, Google might slap your website and then it's gonna be bye bye rankings and traffic.