Northcutt has provided an excellent complete guide about Google Ranking factors. (Click on the above link to view)

There’s a lot of information floating around these days about what makes a site rank higher in Google’s free5, organic listings. Through our research, we’ve found the majority of this advice to be either partially wrong or completely wrong. The advice and products stemming from that information are often dangerous. And finally, the accurate “factors” remaining often aren’t factors that Google considers at all, but tactics and indirect correlation.

Despite all that, we actually know a lot for certain about the way Google ranks web sites. Real SEO knowledge doesn’t come from a random blogger, forum, or magic “get rich quick” scheme. The most trustworthy SEO knowledge only comes from three sources.

Patent filings

Direct statements from Google and/or their team

Applying The Scientific Method

This resource is a complete guide to how Google ranks sites.15 We’ve included factors that are controversial or even outright myths, but created filters so you can sort out concepts that are less-substantiated. This resource is also limited to what factors matter when ranking in Google’s primary web search for non-local requests. This is important to clarify since local SEO, image-only search, video search, and every other Google search engine plays by at least slightly different rules.