Google has been quoted as saying that their search algorithm takes into account over 200 signals (or variables) to determine the ranking of a page for a given query. This isn't really news to anyone who has been paying attention but it should change how many approach search engine optimization (SEO).
Of course some of the 200 signals are weighted more heavily than others, but Google can twist the knob up or down on each of these to dial in what they believe are the most relevant results. As such, concentrating on a short list of critical search engine optimization components will only get you so far.
Don't get me wrong, you must get the short list right, but if you stop there you're likely going to chase the algorithm instead of ride it.
Search engine success by a thousand optimizations.
You might have heard of the saying 'death by a thousand cuts'. The inverse is true for search engine optimization. Success can be attained through doing a lot of little things right. Use natural language to name your images. Change the anchor text or nofollow extraneous 'see more' links. Bold your targeted keywords within your content. The list goes on and on.
I'm often asked to provide a potential return on investment for undertaking a small SEO effort. Yet, it's nearly impossible for me to assign that value. Will it help? Yes. How much? I don't know. Why don't I know? 200 signals! And it's not just the sheer number of signals but the fact that the weighting of those signals changes.
For example, I see more and more sites abandoning meta keywords altogether. I believe this is a mistake. While the weighting for meta keywords might be very low now due to high abuse, it is still one of the signals. There remains some criteria in place for analysis. At any given time Google could determine that the proverbial 'coast is clear' and begin to increase the weight of meta keywords once again.
Follow blind five year old principles.
My philosophy is to treat search engines like blind five year olds. As such, I think of these 200 signals as hints that I can provide to help it make a decision. The goal is to provide the search engine with as many hints as possible, keeping in mind that they must also be good hints. (Providing a whole bunch of mediocre hints will likely have the same impact as a handful of really good ones.)
But if that five year old is putting a puzzle together I need to make sure I show it the edge pieces and flip over the pieces of, say, the Austrian Castle to make it easier. That will go a long way. But what if I can also sort out the sky from the grass and even begin to group them into different hues?
Suddenly, it's a lot easier to complete the puzzle.