With the roll-out of Panda the user experience becomes a large part of the equation. Panda is a combination of ranking factors which take into consideration high quality content over low quality content. There are various factors that lead the crawlers to consider content quality and one of them is popularity.
Professional Site
Create a professional, interesting, informative site that makes users want to visit, and share. Create a site that is well designed. Include relevant well written content along with corresponding quality interesting visual media.
Each page's structure and labeling should clearly indicate its purpose and relevancy.
Page Structure
The search engines should be able to recognize what your site is about from each page's structure and all of the pages in relationships to each other.
Internal links should indicate the relevance of one page to another
Labeling is important - meaningful file names that indicate the purpose of the page
Meaningful headings
Meaningful lists
Page Theme
For each page stay within a theme/topic. The crawlers try to recognize distinct topics which add up to an overall theme. Staying within the same theme will also make your site more coherent to users.
Popular Site
An interesting site will make your users want to stay longer (which will lower your bounce rate) and return often. Both of which will improve your site's popularity. Quality content will also encourage reputable inbound links (back-links) to your site.
Advertisements
The content should far out-way the amount of advertisements that are on any one page.
