Use H1, H2 and H3 to wrap headings that contain page keywords.

The HTML specification says that the heading tags (H1 through H6) are used to describe topics of text sections. However the first three heading tags (H1, H2, H3) also have important SEO implications for the pages that use them. All major search engines (Google included) give higher precedence to text enclosed in H1, H2 or H3. H1 has the highest importance and H3 has the lowest priority, but still text inside it has more weight than plain text).

We recommend you to have at least one H1 tag per page, optionally with one or more H2 and H3 tags. Place keywords-rich content in the H1, H2 and H3 tags, with the most important keywords in the H1 tag and the less important ones in the H2 and H3 tags.