Still on the subject of website grading tools: Via the growing and very useful resource Similar Sites I found the site Website Grader.

Tools such as these are great because you can not only put your own site in there and track its progress SEO-wise, you can also look at other sites and learn from their failures and successes.

Also, each of these tools seems to have a slightly different emphasis. So, like a patient with a mystery ailment getting a second, third or even fourth opinion, you end up with a finer and more nuanced assessment of the state of your website.

Also, they all have explanatory notes attached to each aspect that they're assessing. When combined these descriptions constitute a pretty good roundup of recommended SEO practises. Just reading through these is illuminating - almost like having a brief but comprehensive lesson in basic SEO.

There are more and more free seo tools out there.Two good ones I have found lately are Woorank and SEOBugs. They both do much the same thing: type in your URL and these sites will analyze several key aspects of your website and give you an assessment. This is useful information, since you can get a good general idea of what you're doing right and wrong. Then you can easily make those basic changes that need to be made.