A lesson is a lesson. What precisely is a trial lesson?
If this is a potetential candidates first flight then surely you should be aiming to set the scene for the remainder of the course. You are the salesman selling a product that is going to keep you in business.
Complex briefings before a first flight go clean over the candidates head. Get them into the air and show then that after 15 minutes they can actually fly - then they'll be back.