You can use tools like WordPress SEO (created by Yoast): http://wordpress.org/extend/plugins/wordpress-seo/ to improve your seo. It will generate a sitemap for you and you can change the title and meta tags (including facebook og meta tags) for each entry. It will also handle the robots meta tag.
Personally I'd delete following line from header.php:
if (function_exists('avia_set_follow')) { echo avia_set_follow(); }
and change following line:
<title><?php bloginfo('name'); ?> | <?php is_home() ? bloginfo('description') : wp_title(''); ?></title>
to:
<title><?php wp_title(''); ?></title>
- the reason is that WP SEO will give you full control over the title and you don't need to use Kriesi's default title structure.