This post explains three types of “ranking factors” widely believed to be important to Search Ranking at both Google and Bing. These are:
1) On-site factors: What are the words on your page and how do they relate to the keywords in the search. The search engines look at the code of your webpage. Can they find keywords in that code. Are the keywords found in places that the search engine thinks are important? Is the url of your page one that implies that the page is “on target” for the search?
2) Off-site factors: What sites link to your site and to the pages of your site? What keywords are in the link text that is clickable in those links? The most talked about example is Google PageRank. PageRank is a number that Google shows for a given webpage that shows in very rough and generic way how much “link juice” a page is understood by Google to have. Generally speaking, if a page has more links from many different reputable sites, it will have more PageRank and will have a better chance of ranking for searches.
3) “Keyword Agnostic Signals”: This is a relatively new addition to ranking factors and in some ways it overlaps with Off-site factors. Keyword Agnostic signals are things like the amount of traffic occurring at the website, the success rate of the website for engaging visitors, social mentions for the website , site speed, the age of the domain, the freshness of the content.
Do you have to score well on all three of these to rank? It depends how competitive the ranking is for the particular term (keyword phrase) you are asking about. Some phrases are much more competitive than others.
How can you tell which factors are the most important? Most professional search professionals learn from trying things and from reading what other people are saying. Matt Cutt’s blog (http://www.mattcutts.com/blog/) is a very valuable resource since Matt is “on the inside” at Google. SEOMoz.com has an annual survey of SEO luminaries which is an important reference to the leading thinking in SEO. Check it out at http://www.seomoz.org/article/search-ranking-factors.