Well, we have already installed our new Drupal site and after getting into matter we can take a look and see how we can prepare our brand new site to help search engines knowing which is the content of our site (that's indeed what is called SEO).
Some things search engines like are maps of your site (sitemap) clean urls (as we did here, our site is prepared for clean urls but this does not mean our nice - node/x - urls are very clean and meaningful).
Let's go step by step: