Malcolm Gladwell, author of The Tipping Point and Blink, has an interesting article in the most recent New Yorker debunking police profiling of violent offenders. He basically argues that their methods are unsound, but that this is concealed by the same kind of cheap psychological tricks used by telephone psychics. In particular, the article discusses a set of tactics described by Ian Rowland: a magician and the author of a book on cold reading.
The tactics included focus on calculated vagueness, exploitation of known or highly probable information, and mechanisms for reducing the chances of being decisively proved wrong. The last of those is particularly crucial, as it can allow you to retain your reputation despite the inevitability of making some incorrect guesses.
Be advised that the article has graphic content.