According to the world's leading SEO professionals, the top ten factors that Google considers when calculating your site's relevancy to a search query, are as follows:

- Keywords in the "Title" tags of your pages
- Incoming link titles
- Overall quality and quantity of links pointing to your site
- Your site's age
- Linking pattern of your site's internal pages
- Relevance of your site's incoming links to its niche
- Quality and quantity of your site's inbound links in its particular topical community
- Keywords in page content
- Overall link popularity of the sites pointing to you
- Relevancy of the page linking to your particular topic

This information is provided in more details on the pages of such authoritative resources as Wikipedia and SEOmoz.