Katsushi Kawamori

<h4>Add OGP tags</h4>
<ul>
<li>“title” displays the title of the site if it is a homepage, otherwise it displays an article or category title.</li>
<li>“description” displays the tagline of the site if it is a homepage or category, otherwise it displays an article excerpt.</li>
<li>“url” displays the permalink of the site if it is a homepage, otherwise it displays an article or category url.</li>
<li>
<p>“image” “post thumbnail” is displayed if present, otherwise the default image is displayed.</p>
</li>
<li>
<p>Can specify the number of characters for “description”.</p>
</li>
<li>Can specify the default image for “image”.</li>
<li>Can specify the X(Twitter) user name.</li>
<li>Can specify the Facebook App ID.</li>
</ul>


Ogp Plus

ShinichiN

<p>When shared on Facebook, this plugin shows a nice Thumbnail of your posts, pages and site.</p>
<h3>Example of Open Graph Protocol tags</h3>
<pre><code><meta property="fb:app_id"      content="you can specify in admin" />
<meta property="og:title"       content="Post Title" />
<meta property="og:type"        content="article" />
<meta property="og:url"         content="Post URL" />
<meta property="og:image"       content="Post thumbnail, attached image, the first image or default image which you upload" />
<meta property="og:site_name"   content="Site Title" />
<meta property="og:locale"      content="Your Locale" />
<meta property="og:description" content="Post excerpt or text generated from your content" />
</code></pre>
<h3>Rules of the og:image</h3>
<h4>When a post permalink is shared (is_singular).</h4>
<ol>
<li>If your post has a post-thumbnail, that will show up.</li>
<li>If not, this plugin shows the images attatched to the post.</li>
<li>If not, this plugin shows the images which is in the content.</li>
<li>If not, this plugin shows the default image, which you upload in Settings > Reading > OGP Settings.</li>
<li>If not, this plugin doesn’t show anything. (Other ogp tags such as og:title, og:url and so on will be served.)</li>
</ol>
<h4>When the link posted on facebook was not a post link (!is_singular).</h4>
<p>When home page, archive pages, search result page or what ever else pages are shared on facebook, og:image will be the image you specify in Settings > Reading > OGP Settings.</p>


OGP Generator

When shared on Facebook, this plugin shows a nice Thumbnail of your posts, pages and site.

Ogp Plus vs OGP Generator