Google Results are based on 4 major criteria
* Keyword Density
* Keyword prominence
* Page rank or back links
* Last, but the most important: Content

Keyword density
The density of keyword affects the ranking of your page. The higher the keyword density the higher is your rank so one should always include a 30-40 word paragraph containing key-word rich content, thus increasing the keyword density.

Keyword prominence
The keywords you have chosen should appear in title, Meta and H tags with some occurrence in the body also. So you should not define Google without putting the word Google in the body of the definition. This means H and P tags should go hand shaking with each other.

Page rank and back links
The more site links to your site better is the page rank of your site and more relevant your site is. Google also takes into consideration the words [or Anchor text] that appear in your back links
Code:
<A> Click Here</A> is less relevant than
<A> Example of Google</A>


Content
Some say that the Content of your site is the king, but for me it’s actually the crown which the webmaster wears if his site has the right content. Build the content and users will be interested just be reading it.