Many people rely on headings to interpret the structure of the page. Without them some people (e.g., screen reader users) cannot easily browse the contents of the page (e.g. by skipping to and reading just the headings).
Provide structure with <h1>, <h2> ... <h6>
All pages should include <h1> for the primary page heading
There should only be one heading coded with <h1> on a page
Avoid skipping levels, e.g. <h1>, <h3> should not follow sequentially, if possible
Style with css - don't use presentational markup to simulate headings
Don't use heading markup just to produce presentational effects (if they are not headings)