Here’s a video of Matt Cutts from Google answering a question about what SEO tactics to focus on for 2011. It was meant for large corporations but applies to most web sites.
In the video Matt covers a few tactics including…
Check your site speed.
First and foremost site speed is an important usability factor that affects your conversion rates, but as Matt says it’s also a “slight” factor in rankings
Get Started – See Google’s Webmaster Tools / Labs / Site performance for a Performance overview of your site and a Page Speed tool you can add on to Firefox
Get Control of Your CMS
Matt talks about the importance of having control of your Content Management System.
See for “How To Improve Organic Search Results With A Simple Site Audit” for more on CMS issues that affect SEO.
Internal Links Consistency
Matt discuses the importance of checking your internal links for 404’s for example, but more importantly chekcing the site’s linking structure; a strong ranking signal.
See 9 Step SEO Checkup Using Google Webmaster Tools , the “Gain Insight Into Link Strategy” section to help get started on internal linikng.
Participate In Social Media To Help Increase Incoming Links
Matt talks about participating in social media because if can help increase the number of high quality incoming links which helps improve your site’s rankings.
Start learning about Link Building here Link Building Basics: What is Link Popularity?
Read between the lines. Would Matt Cutts suggest social media marketing as one of the most important of three or four SEO tactics because of the affect it can have on incoming links? Or would Google like to prod us along on social media marketing for other reasons such as the realization in light of the Panda update that they need social signals to help evaluate what are high quality sites as well as the soon to be released Google +1 social bookmaking/recommendation button?