Effective search engine optimization is equal parts art, science, and EXPERIENCE. Search Engines have become very adept at listing fresh content. The Search Engine Marketing community used to say wait 90 days to see the results. Some changes can occur much more quickly now. Personalized search also throws a large monkey wrench into seeing changes in the SERPs.
http://www.searchenginejournal.com/seo-wins-sins-joe-laratro/18335/
Traditional SEO has centered around moving one web site higher in the search results. The latest forms of SEO such as SEO Monopoly center on moving multiple sites higher in the search results.
