Be with the people. Walk toward and away from the audience as well as left and right to help break down the implied barrier. Avoid rooms with a platform. Tell them you will deal with their question after class because it is a detail, tangential, has a long answer, has already been explained, or you have to think about it. In any event, do not annoy the others by getting sidetracked into something.
Props Use props.
If you are talking about vision, show pictures. If you are talking about force sensors bring one. Take along a few blocks if your talk is about the blocks world. Unroll a giant check-plot of an IC if you have been working on design aids. You need something to do occasionally when you want to stop and think.