Google's Ranking factors

On-Page (Keyword-Specific) Ranking Factors
Keyword Use Anywhere in the Title Tag
Keyword Use as the First Word(s) of the Title Tag
Keyword Use in the Root Domain Name (e.g. keyword.com)
Keyword Use Anywhere in the H1 Headline Tag
Keyword Use in Internal Link Anchor Text on the Page
Keyword Use in External Link Anchor Text on the Page
Keyword Use as the First Word(s) in the H1 Tag
Keyword Use in the First 50-100 Words in HTML on the Page
Keyword Use in the Subdomain Name (e.g. keyword.seomoz.org)
Keyword Use in the Page Name URL (e.g. seomoz.org/folder/keyword.html)
Keyword Use in the Page Folder URL (e.g. seomoz.org/keyword/page.html)
Keyword Use in other Headline Tags ( - )
Keyword Use in Image Alt Text
Keyword Use / Number of Repetitions in the HTML Text on the Page
Keyword Use in Image Names Included on the Page (e.g. keyword.jpg)
Keyword Use in or Tags
Keyword Density Formula (# of Keyword Uses ÷ Total # of Terms on the Page)
Keyword Use in List Items on the Page
Keyword Use in the Page's Query Parameters(e.g.seomoz.org/page.html?keyword)
Keyword Use in or Tags
Keyword Use in the Meta Description Tag
Keyword Use in the Page's File Extension (e.g. seomoz.org/page.keyword)
Keyword Use in Comment Tags in the HTML
Keyword Use in the Meta Keywords Tag