I use the devil's advocate approach to gathering software requirements. I argue against what I feel are good ideas and argue for what are seemingly not so good ideas. As long as you don't get too far off track the discussion is often very enlightening about what your customers actually want to build. The downside is that you either end up feeling like or looking like an idiot because you're seemingly on the wrong side of idea (BTW I'm not claiming that I'm not an idiot). Letting everyone know that this is your approach doesn't have much, if any, downside and alleviates this problem. Having another person to tag team with makes it less exhausting. It works for the same reason that Stern's approach works - people love to tell you how you are wrong.