"We're going to play a game of chess, and I'm going to beat you at it. In fact, I'm going to beat you at chess in such a fashion that the mental trauma of losing so badly will alter your personality type forever. Then I'm going to explain how I did it, because I know you were wondering how someone could be so great at chess like that. Upon your departure as a completely different type, I will review my stock profits for the day."
If you've ever played the game "Clue", this will be the same way. Pretend to be a certain type in this thread and interact with other members (ex. ask questions to gather information on them). Identify other posters' type once you think you know it, which they can confirm or deny. Once someone correctly guesses your type you can pick another one to become.