Search engine optimization overall strategies change over time. The individual tactics may be constant, but how much effort you put towards each constant changes. For example, 5 years ago it may have been about creating lots and lots of content. 2 years ago it was more about link exchanges and getting any link and a lot of them. In 2005 it was more about getting better quality links. In 2006, what will be the major force of gaining long term search rankings in the engines?
That is the topic of a new thread at Search Engine Watch forums named SEO/SEM Tactics For 2006. As you can see from the thread, much of the 2006 predicted effort is going to go towards user centric patterns. Most SEO/SEM companies are going to begin (if not already) applying their focus to creating a better user experience, improving user trust, increasing non search generated traffic to a site and keeping users on a site longer.
The thread is a nice one, so check it out at Search Engine Watch Forums.