I'd be interested in similar discussion on what rotary FIs do on trial lessons.
I've come to the conclusion that here too flexibility is the key. I sit the new student down and ask what they want to do. I also find out their previous experience - have they ever been in a light aircraft, have they ever been in any aircraft, have they ever taken control, have they ever been in a helicopter. It gives me an idea if they're likely to panic, and even if they'll need a few minutes to get used to the experience. As for briefings, recently I've started doing them IN the helicopter. It saves that glazed expression when you first draw a T-bar cyclic on the board, and makes it all less strange and potentially scary. After that it varies tremendously, depending on what they want and how good they are. But since a very keen, very quick-learning student got airsick, I'm tending to slow things down a little more than I used to, even with the people who pick it up fast.
What do the rest of you do?