Josh Berkus, one of the core developers of PostgreSQL, gives a tongue-in-check talk on 10 ways to wreck your database.
The talk is about 40 minutes long -- a decent enough talk. However, the Q&A portion that followed the talk is stellar. Unfortunately, you can't really just skip to the Q&A portion and you definitely don't want to stop watching after the talk because you would get the wrong impression.
The most important point for me was that I need to start using natural keys in my database and normalized through natural keys rather than primary keys.