So hold on - the most important factor always gets the least amount of air time? Why is that?
My guess is that the things you can control are many, they are somewhat technical, and so they make site owners feel they need the services of SEO gurus. At the same time, the "external factors" are few, easily understandable, and take a lot of time and effort to get right. And you can probably do a better job in this area than your consultants could anyway.
I'm not saying that keyword research, meta tagging, etc are not important - they are. But those are just table stakes. If you want to differentiate your site, you have to focus on the external factors, and spend the time and effort to get this area right.
So what is it you should be doing? Here is a list of possible activities:
- Find the most influential (i.e., highest ranking) sites that publish about the same subjects as you do on your site. If you make widgets, find out who publishes the most influential reviews of widgets, who posts educational content about widgets, who the biggest users are of widgets, etc.
- Review your content to ensure that it will be seen as having value to those influential sites.
- Build relationships with the influential sites' publishers. Show them who you are. Convince them of your authority in your shared market.
- Build out your online relationships with these publishers. In other words, you want them to understand that linking to content on your site will enhance their content. At the same time, if they have content that your site visitors would value, be sure to link to it.
- Use your relationships to find out what content they - and their visitors - want. If it's something that you can provide, and that will build your reputation or make people interested in you, develop that content - and let the publishers know when you have done so.
Here's a good article on this subject: http://sites.google.com/site/howtoseo/seo-3-external-ranking-factors.