Study html, and proper coding of web pages - this is no secret. This was the purpose of <h> tags from the beginning. Everybody thinks it was for appearance only but not so. It was to properly organize your text to maximize organization for the web.
The internet runs on visuals but is indexed by plain text. <h> tags, alt and title attributes, meta-tags and, of course, text which are all congruent will greatly assist people finding you for your exact content. This is the sort of stuff SEO companies charge people a lot for. They always "alter" the page and these are a few of the things they pay attention to.