Facebook preview Open Graph Object Debugger

Try this: In your functions.php put this

function fb_excerpt($text, $excerpt) {
    if ($excerpt) return $excerpt;

    $raw_excerpt = $text;

    $text = strip_shortcodes( $text );

    $text = apply_filters('the_content', $text);
    $text = str_replace(']]>', ']]>', $text);
    $text = strip_tags($text);
    $excerpt_length = apply_filters('excerpt_length', 55);
    $words = preg_split("/[\n\r\t ]+/", $text, $excerpt_length + 1, PREG_SPLIT_NO_EMPTY);
    if (count($words) > $excerpt_length) {
            array_pop($words);
            $text = implode(' ', $words);
            $text = $text . '...';
    } else { $text = implode(' ', $words); }

    return apply_filters('wp_trim_excerpt', $text, $raw_excerpt);
}

and in your header.php between you <head> and </head> tags put this

<?php global $post;
if (is_singular()) { ?>
    <meta property="fb:admins" content="522774907844630">
    <meta property="og:title" content="<?php the_title(); ?>">
    <meta property="og:description" content="<?php echo fb_excerpt($post->post_content, get_the_excerpt()); ?>">
    <meta property="og:type" content="article">
    <meta property="og:image" content="<?php echo wp_get_attachment_url(get_post_thumbnail_id($post->ID)); ?>">
    <meta property="og:site_name" content="<?php bloginfo('name'); ?>">
    <meta property="og:url" content="<?php echo('http://'.$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI']); ?>">
<?php } ?>