include em, strong, h1, h2, h3, h4, h5, and h6. These tags change the look of the page, but more importantly, give meaning to page items. CSS will be used to style the page (change the presentaton), not html.
include ol, ul, li, table, tr, and td. These tags help change how information is presented on the page, with emphasis on meaning.
Again, HTML is meant to display information in black in white text. CSS is meant to style your information so it looks good.