Get trained by Paul Ekman. He's a leading scientist in the field of micro-expressions - those subtle face movements we all make that hint at the veracity of what we're saying. His F.A.C.E training website has a demo you can run that will test your current skills.
Coaching - the really good kind - is hard work. To prepare for the challenges involved, it only makes sense that people train to become coaches. This is a great resource - for coaching youth sports or even employees.