Paul,
Google is famous for relying on links.
To find a complete answer your question, you will want to check out this site:
http://www.searchenginewatch.com/
Also, if want to understand how search engines work, read the series of articles found at this site:
http://www.tbray.org/ongoing/When/200x/2003/07/30/OnSearchTOC
Trusting this information is of some value in your quest.
Kind regards,
John Glube
Toronto, Canada
How To Increase Traffic To Your Site Without Spending Advertising Dollars