The very easiest way for you to do it (Without a plugin) is to enter Serendipity Configuration and turn on embedded mode.
Then open your templates/layout.php in the template you created (or use templats/default/layout.php if that file does not exist in your directory).
Then also open the file serendipty_genpage.inc.php - there you'll see all the HTML headers. You can copy them (with the PHP-Variables) and insert them in your layout.php file.
Your layout.php needs to contain html, head and body tags, and body+html need to be closed at the bottom of layout.php...
# Garvin Hicking (s9y Developer)
# Did I help you? Consider making me happy: http://wishes.garv.in/
# or use my PayPal account "paypal {at} supergarv (dot) de"
# My "other" hobby: http://flickr.garv.in/
I've noticed Dublin Core tags for individual entries. How about Dublin Core for the main page in the head section drawing from latest update, page title, owner, home directory that are found on the 7.1 info page?