CSS Overview and Drupal Q&A

It's not that CSS is such a simple topic that it will only take 30 minutes to cover in depth - It's that there's so much to cover that I'm not sure how to tackle it without rambling from subject to subject. I'll talk about critically important concepts like specificity, inheritance and the box model and such, but after that, what's the best use of our time? Any suggestions on how to focus this discussion would be appreciated.

If I understood correctly, for the rest of the session we'll attempt to tangibly tackle user's Drupal questions by starting with a fresh, local installation.