For me it's always been the idea of establishing a commonality first. When people enter negotiation they almost always have their guard up. "They are thinking how is this guy going to pull one over me?"

If you manage to successfully remove that fear, become a normal human being right in front of their eyes. Sometimes by simply discovering you both like the same music (it can be that simple) the barriers come down, and a true connection/conversation can start.

So it's a trick, but it's more like a practice of balance.