I talk at conferences a lot (like 20 presentation in May/June much), and I know I've done it right when I get a lot of questions. If I don't get any questions,

I talk at conferences a lot (like 20 presentation in May/June much), and I know I've done it right when I get a lot of questions. If I don't get any questions, I go back and review my material because questions means that people's brains are working and no questions means that for some reason I switched everyone in the room off.