This is related to Explain in SO FAQ concept of accepting answers, but is a more specific feature request.
Please add a paragraph to http://stackoverflow.com/faq showing that one accepts an answer by clicking the check mark. I've seen posts from people who really didn't know that's what the symbol meant - perhaps it doesn't mean "yes" in all cultures?
You might also show a picture of a user block with low accepted answers, and show the relationship between the two.
On the site, I drive users towards reading the FAQ. It would be good if the necessary information were right in the document, and not just links to another site they don't have time to read.