Be the search engine
Sometimes when I think of SEO I imagine what the search engine sees. There are a couple of nice “search engine”-like sites that strips your page from HTML tags. But to be really good at SEO we need to see the core of each tag. The engines are looking for tags that it recongizes. The HTML standard has tags that all have a purpose. And as a SEO person I need to know which tag to use when. For example, a table is for displaying data. Not organizing a menu. We use the UL > LI tag for that.
It all makes sense. Think about which tag to use and when. With CSS the user don’t even need to know which tags are in use. But the Engines needs to know!