<?php
    // Setup Meta Variables
    global $post;
    $categories = get_the_category($post->ID);
    $post_title = single_post_title('', FALSE);
    $site_title = get_bloginfo('sitetitle');
    $category_title = $categories[0]->cat_name;
    $site_description = get_bloginfo('description');
    $forum_description = "Custom forum description";
?>

<?php
    // Forum Board Meta Tags
    if(get_post_type() == 'forum') {
        if($post_title <> "") {
            $post_title = $post_title;
        }  else {
            $post_title = "Custom post title";
        }
?>
        <title><?php echo $site_title; ?> - <?php echo $post_title; ?></title>
        <meta name="description" content="<?php echo $site_title; ?> - <?php echo $post_title; ?> - <?php echo $forum_description; ?>" />
        <meta name="keywords" content="<?php echo $site_title; ?>, <?php echo $post_title; ?>, keyword, keyword2, keyword 3" />
<?php
    // Forum Topic or Reply Meta Tags
    } else if (get_post_type() == 'topic' OR get_post_type() == 'reply') {
?>
        <title><?php echo $post_title; ?> - <?php echo $site_title; ?></title>
        <meta name="description" content="<?php echo $post_title; ?> - <?php echo $site_title; ?> - <?php echo $forum_description; ?>" />
        <meta name="keywords" content="<?php echo $post_title; ?>, <?php echo $site_title; ?>, keyword, keyword2, keyword 3" />
<?php
    // Else, wordpress pages/posts meta tags
    } else {
        // Home page specific meta tags
        if (is_front_page()) {
?>
            <title><?php echo $site_title; ?> - Custom homepage title!</title>
            <meta name="description" content="<?php echo $site_title; ?> - <?php echo $site_description; ?>" />
            <meta name="keywords" content="<?php echo $site_title; ?>, keyword, keyword2, keyword 3" />
    <?php
        // Else, posts, pages and categories
        } else {
    ?>
            <title><?php if($post_title <> "") { echo $post_title . " - "; } else { echo $category_title . " - "; } ?><?php bloginfo('sitetitle'); ?></title>
            <meta name="description" content="<?php if($post_title <> "") { echo $post_title . " - "; } else { echo $category_title . " - "; } ?><?php echo $site_description; ?>" />
            <meta name="keywords" content="<?php if($post_title <> "") { echo $post_title . ","; } else { echo $category_title . ","; } ?>, keyword, keyword2, keyword 3" />
    <?php } ?>
<?php } ?>