What Open Graph is for Facebook, Twitter Cards are for… well, Twitter:

Twitter cards make it possible for you to attach media experiences to Tweets that link to your content. Simply add a few lines of HTML to your webpages, and users who Tweet links to your content will have a “card” added to the Tweet that’s visible to all of their followers.

While Facebook parses Open Graph tags from every page, you have to sign up for Twitter Cards.

Before you do that, you need to have properly working Twitter Cards metatags on your page, which is fortunately not that complicated – either follow their instructions for your CMS or enjoy the fact that you are using WordPress and install Niall Kennedy’s Twitter Cards plugin. If you’re lazy like me and don’t want to fiddle around with your theme’s function.php, just use my Twitter Cards Enhancer plugin which includes the tags automatically. To get the proper attribution tags, you’ll have to fill out two (new) fields in your WordPress backend, though:

Put your blog’s twitter account under “Settings”:

And each author on your blog should put their twitter account under “Users” → “Your Profile”:

Once you’re done with that, use Twitter’s test tool and apply for inclusion. When everything works out as intended, tweets that include your posts will start to look like this:

Or probably better.