SEOmoz has published their 2011 top search engine ranking factors, based on feedback from 132 SEOs around the world and by correlating data from over 10,000 Google results

What is interesting is that page level links and keyword usage, as well as domain level authority account for over half of a page’s “Google Juice” and searchability.

The following table shows the impact of individual factors on an individual page’s ranking on Google:

It helps to have a search keyword as the first word of the page TITLE, and to repeat it often in the content of the page, to use it in the H1 tag (don’t use <p class=page_title> CSS style tags!), use that phrase in image ALT tags, as well as in the META KEYWORDS tag, and also  important, keep those keywords close to the top of the page coding.

This last factor penalizes pages which use bad layout (using raw pages created by drag & drop coding tools like DreamWeaver, without tweaking) or do not optimize their CSS (using all-purpose templates and not getting rid of styles not used on your site/page). Laziness in web designers (or their amateurishness) is penalized by Google!

Shifts in Google Ranking Factors

This table shows have factors are increasing in importance (orange, on the right) or declining (grey, on the ldeft):

What is interesting is the growth of “social factors” at a page and domain level, as well as the strength of  factors like page usage (clickthrough and bounce rates) ,  content readability & design, and the ratio of advertising  to content. Also important is the relative declineof importance of factors like exact match of keywords in domain names, and the effectiveness of paid (ie, adWords) links.

View Complete Factors (SEOmoz)