Search engine optimization is a very important aspect of building Web Sites. Because search engines criteria for ranking web sites like google are not public,, there is a lot of speculation on some aspects of optimization. What complicates things is that what worked last year does not necessarily work this year. For example, google recently said they would penalize over-optimized sites... as of the writing of this article, no one is really sure what it means (if anything) to current SEO techniques.
Further, what works with one engine does not necessarily work on another... for example, Google mostly ignores meta tags for its ranking while other engines or directories greatly depend on it to control what is displayed.
Another aspect to keep in mind is with the advent of social networks, the way to drive traffic to a web site has changed. Optimizing a web site is not only about ranking number one in engines but engaging potential visitors in a whole new set of ways like facebook pages, twitter and whatever the current vector en vogue is.
However, as daunting as adapting to change seems, a lot of the tried and true concepts remain the same and the changes are usually incremental.
If you are new to SEO and online marketing, welcome to the club... if you are a veteran, you are welcome to add your grain of salt @theseobell on twitter