I took the time to write up a best practices wiki page on the Nginx wiki for Drupal. Your configurations may or may not be similar and may or may not add extras. The setup in the Nginx wiki will not cover things like using Boost or Varnish.
The configuration in the wiki will provide an excellent base for anything you want to do with Drupal (and Pressflow). It takes a lot of beginner mistakes and explains why they are the wrong way. There are a massive number of beginner mistakes that I've seen around drupal.org and the rest of the Internet. I hope that linking to this page will help.