I spent the better part of the day learning how to add social share buttons to a site since it can “increase inbound traffic by up to 149%.” I found, much to my chigrin, that each of the various social networks handle their share API very differently.
 Here are a few of the resources I found that helped me simply add the button or at least helped me get started plugging into the API:

Facebook

developers.facebook.com/docs/reference/plugins/like/

Twitter

twitter.com/about/resources/buttons

Google +1

www.google.com/intl/en/webmasters/+1/button/index.html