Drupal Multisite allows you to have one set of code and each subdomain (or domain) has its own database and its own theme. I set up one subdomain the way I'd like to be the base for all subdomains and copy it when I create a new subdomain. Then I customize the new subdomain with its specific settings and theme. First, I'll take the participants through setting up a multisite setup. Then I'll copy the initial database and customize a new subdomain using it. This presentation is excellent for those wanting to know more about multisite and also for beginners becoming comfortable with setting up a new site using an existing site as a base.