Getting Facebook to show preview images

I noticed that Facebook wasn’t showing any preview images for a website I maintain (, my pet grey tribe political party/think tank). It turns out that Facebook wants a metatag to know which image to use: og:image. And how does one get this? Fortunately, there are some simple WordPress plugins to handle this issue. After one has added this, go to this page and rescrape the site. Then it should correctly show the preview image.