Advanced search engine optimization is simply a matter of learning & applying the knowledge that already exists on the web. Cutting edge SEO, however, requires massive research and testing, and is beyond the scope of this article (although SEOmoz does conduct research and analysis studies - available in the advanced topics section).
The best way to begin learning advanced optimization techniques is to start applying the basics to your website. From the nascent beginnings of optimization, you will find hundreds if not thousands of questions that need answering. Most of these are not specifically addressed in any single resource, but can be found on most of the major SEO forums.
Search Engine Watch
Advanced SEO requires delving deeply into the process of the search engine's algorithms. Much of this knowledge can be derived from watching the SERPs carefully from day to day and over the long term. Creating careful analysis reports that compate your site against the top 20 sites for a specific topic phrase are especially useful. There are literally hundreds or thousands of ways to keep up-to-date with the SEO world and the practice of optimization, but none are better than working diligently at the optimization of your own site.
When seeking out the latest SEO news & industry-related topics, however, the following sources are invaluable and should not be ignored by anyone seeking to gain a deep, thorough understanding of search optimization: