If you haven't yet, I'd suggest following the link on the last page for the dA anatomy tutorial. There's a set of links at the bottom of that page labelled "Manga to Realistic" which is mostly concerned with drawing realistic faces, assuming a cartoon-style starting point for most incoming artists. Although I don't really draw much in a manga style, the tips are pretty generically useful, and one of the later tutorials goes specifically into how the face moves in different facial expressions. There was also a neat section on thinking about how to draw different ethnicities, to break out of the Caucasian/Asian box lots of people can get stuck in.
I would link the page directly, but I'm at work and can't go link-hopping just yet >.>
Oh, also the grammar is a bit dodgy, but I think that's because the artist is ESL; the pictures tell most of the story anyway. Thought I should warn you, since I didn't know if that would trigger any of your writer buttons.