If you came here in search of the Google search engine algorithm, here is a word of advice. Without turning this into a theoretical post based on heuristic conclusions discovered over the course of 10 years of trial an error. Put simply, it relies on content and reputation to determine relevance.
If you are still waiting for the magic bullet for search engine optimization in order to achieve the ultimate competitive advantage, then it is time to change the way you view the function of relevance.
Optimization implies removing unnecessary obstructions that prevent search engines spiders from determining the value of your content. If the information provided on your pages has true objective value for your industry, then it will inherently have greater appeal to search algorithms whose prime directive is to return the most relevant result.
Not that opinion, rants or less descriptive topics are not entertaining, however if authority for your pages is the objective (the ability for every page to have the ranking and regard of a wiki) then providing densely grouped facets of topical information can establish authority for your content and inevitably your site.
Writing for writings sake is great, if you just want to have a small ripple effect. To make a splash however, and reach a larger audience theming your content to increase site-wide relevance vs. harboring multiple topics is one method to project the appropriate signal.
In addition, value is determined by engagement traffic determines who stays in the top 10 and who slips off into a less dominant position. The benefits of an aged domain with authority are unparalleled.
With a mere mention of a topic in the title tag and a sparse stint of reference, such a site can remain in the top 10 for multiple searches as a result of the site architecture and internal links alone.
We will be discussing this topic in greater detail in the following weeks, but in closing, here are a few resources covering the topic of website authority and the different ways to accomplish it involving tactful writing or website promotion.