Here is what I use now, which was provided years ago as an answer from this site. Works Great still!
function get_att_images($args = array()) {
	global $post;
	$defaults = array(
		'format'	=> 'url',
		'size'		=> 'full',
		'num'		=> 0,
		'attr'		=> '',
	);
	$args = wp_parse_args( $args, $defaults );
	if ( has_post_thumbnail() && ( 0 === $args['num'] ) ) {
		$id = get_post_thumbnail_id();
		$html = wp_get_attachment_image( $id, $args['size'], false, $args['attr'] );
		list( $url ) = wp_get_attachment_image_src( $id, $args['size'], false, $args['attr'] );
	} else {
		$id = _get_image_id( $args['num'] );
		$html = wp_get_attachment_image( $id, $args['size'], false, $args['attr'] );
		list( $url ) = wp_get_attachment_image_src( $id, $args['size'], false, $args['attr'] );
	}
	$src = str_replace( home_url(), '', $url );
	if ( 'html' === strtolower( $args['format'] ) )
		$output = $html;
	elseif ( 'url' === strtolower( $args['format'] ) )
		$output = $url;
	else
		$output = $src;
	if ( empty( $url ) ) $output = false;
	return $output;
}
function insert_fb_in_head() {
	global $post;
	if ( !is_singular()) //if it is not a post or a page
		return;
        echo '<meta property="fb:app_id" content="" />';
        echo '<meta property="fb:admins" content=""/>';
        echo '<meta property="og:url" content="' . get_permalink() . '"/>';
        echo '<meta property="og:locale" content="en_US" />';
        echo '<meta property="og:title" content="' . get_the_title() . '"/>';
        echo '<meta property="og:type" content="article"/>';
        echo '<meta property="og:site_name" content=""/>';
	$post_thumb = get_att_images();
	echo '<meta property="og:image" content="' .( ($post_thumb) ? $post_thumb : '/images/generic-logo.png' ). '" />';
	echo "\n";
}
add_action( 'wp_head', 'insert_fb_in_head', 5 );
What I am missing and can't seem to figure out is I need to add the field:
echo '<meta property="og:description" content="" />'; 
I need it to pull from the post or pages content, not excerpt, since I do not use the excerpt field. I would also need it to limit how much it pulls. If there is no content I need it to pull in a generic sentence. 
			
Reigel Gallarde answers:
								try this for your insert_fb_in_head function...
function insert_fb_in_head() {							
	global $post;
	if ( !is_singular()) //if it is not a post or a page
		return;
		
	echo '<meta property="fb:app_id" content="" />';
	echo '<meta property="fb:admins" content=""/>';
	echo '<meta property="og:url" content="' . get_permalink() . '"/>';
	echo '<meta property="og:locale" content="en_US" />';
	echo '<meta property="og:title" content="' . get_the_title() . '"/>';
	echo '<meta property="og:type" content="article"/>';
	echo '<meta property="og:site_name" content=""/>';
	$post_thumb = get_att_images();
	echo '<meta property="og:image" content="' .( ($post_thumb) ? $post_thumb : '/images/generic-logo.png' ). '" />';
	setup_postdata( $post );
	$description = get_the_excerpt();
	echo '<meta property="og:description" content="' .( ($description) ? $description : 'Some generic sentence!' ). '" />'; 
	echo "\n";
}
Reigel Gallarde comments:
										to limit to a certain number of words, you can use wp_trim_words. This function trims text to a certain number of words and returns the trimmed text.
$description = wp_trim_words( get_the_excerpt(), 20, '' );									
Luis Abarca answers:
								You can use if_* tags to generate the description tag.
<?php 
$description = '';
$default_description = 'your text here';
if (is_singular()) {
    $description = get_the_excerpt();
} else if (is_category()) {
    $description = category_description();
} else {
    $description = get_bloginfo('description');
}
if ( empty($description) ) {
    $description = $default_description;
echo '<meta property="og:description" content="' . $description . '" />'; 
twdesigns comments:
										Greetings,
For what ever reason when the get_the_excerpt is used it doesn't pull in data. It's my understanding that if I don't use the excerpt field then it's supposed to pull in X characters stripped from the content. 
My posts are listings with custom fields and the content is about the company. Thus some of my posts have no content and as mentioned I would like to add, if possible, a statement that if no content is available then it use a generic og:description, as mentioned in my original question.
Thanks!									
twdesigns comments:
Can you add this to my existing function. I think it will then solve my issues :)
Luis Abarca comments:
										Sure.
function insert_fb_in_head()
{
	global $post;
	$description = '';
	$default_description = 'your text here';
	if ( !is_singular()) //if it is not a post or a page
		return;
    echo '<meta property="fb:app_id" content="" />';
    echo '<meta property="fb:admins" content=""/>';
    echo '<meta property="og:url" content="' . get_permalink() . '"/>';
    echo '<meta property="og:locale" content="en_US" />';
    echo '<meta property="og:title" content="' . get_the_title() . '"/>';
    echo '<meta property="og:type" content="article"/>';
    echo '<meta property="og:site_name" content=""/>';
	$post_thumb = get_att_images();
	echo '<meta property="og:image" content="' .( ($post_thumb) ? $post_thumb : '/images/generic-logo.png' ). '" />';
	echo "\n";
	if (is_singular()) {
	    $description = get_the_excerpt();
	} else if (is_category()) {
	    $description = category_description();
	} else {
	    $description = get_bloginfo('description');
	}
	if ( empty($description) ) {
	    $description = $default_description;
	}
	echo '<meta property="og:description" content="' . $description . '" />'; 
}
add_action( 'wp_head', 'insert_fb_in_head', 5 );
twdesigns comments:
My issue still remains. When I applied the above it only pulls in the custom text even though the post has content. Suggestions?
Alvaro Rosado answers:
								Edit*
sorry, answered twice.							
Alvaro Rosado comments:
										Try this:
// Function to limit the content words
function limit_content_words($string, $word_limit) {
    $words = explode(' ', $string, ($word_limit + 1));
    if(count($words) > $word_limit)
    array_pop($words);
    return implode(' ', $words);
}
function get_att_images($args = array()) {
	global $post;
	$defaults = array(
		'format'	=> 'url',
		'size'		=> 'full',
		'num'		=> 0,
		'attr'		=> '',
	);
	$args = wp_parse_args( $args, $defaults );
	if ( has_post_thumbnail() && ( 0 === $args['num'] ) ) {
		$id = get_post_thumbnail_id();
		$html = wp_get_attachment_image( $id, $args['size'], false, $args['attr'] );
		list( $url ) = wp_get_attachment_image_src( $id, $args['size'], false, $args['attr'] );
	} else {
		$id = _get_image_id( $args['num'] );
		$html = wp_get_attachment_image( $id, $args['size'], false, $args['attr'] );
		list( $url ) = wp_get_attachment_image_src( $id, $args['size'], false, $args['attr'] );
	}
	$src = str_replace( home_url(), '', $url );
	if ( 'html' === strtolower( $args['format'] ) )
		$output = $html;
	elseif ( 'url' === strtolower( $args['format'] ) )
		$output = $url;
	else
		$output = $src;
	if ( empty( $url ) ) $output = false;
	return $output;
}
function insert_fb_in_head() {
	global $post;
	if ( !is_singular()) //if it is not a post or a page
		return;
        echo '<meta property="fb:app_id" content="" />';
        echo '<meta property="fb:admins" content=""/>';
        echo '<meta property="og:url" content="' . get_permalink() . '"/>';
        echo '<meta property="og:locale" content="en_US" />';
        echo '<meta property="og:title" content="' . get_the_title() . '"/>';
        echo '<meta property="og:type" content="article"/>';
        echo '<meta property="og:site_name" content=""/>';
        
        $content = get_the_content();
        // 25 is the word limit, you can change this.
        echo '<meta property="og:description" content="' . limit_content_words($content,25) . '" />'; 
	$post_thumb = get_att_images();
	echo '<meta property="og:image" content="' .( ($post_thumb) ? $post_thumb : '/images/generic-logo.png' ). '" />';
	echo "\n";
}
add_action( 'wp_head', 'insert_fb_in_head', 5 );
twdesigns comments:
										This pulled in a blank og:description on both posts with and without content through the object debugger from facebook. I'm not sure why it was blank both times as I tested it on several posts with content.
Thanks