Social Media icons make it easy for readers to share the content they find on your blog. One click and your readers can share your posts and pages to a wider audience. (Users will be asked to sign into their social media accounts, if not already signed in.)
The Commons has two WordPress plugins that manage social media icons on your posts, Sociable and Share This. Sociable has a full-featured options panel that allows full icon configuration, including sizes, styles, and placement. Here is a video introduction to Sociable.
Not to be outdone, Share This has some very detailed instructions that can be found here. One nice feature of Share This is that it allows for “Multi-Post” sharing within your blog, so that users remain on your site while they share to multiple sites:
So which to choose? Check them both out and see which one you prefer.