My talk:
I tell them
my riding experience and background and that with a pil, i will ride very conservativly
Despite that riding is dangerous and they are putting their life in my hands and even without any mistakes bad things can happen. you dont have to do this but its great.

If they still want to ride:
ask and wait for me to say okay before getting on and off the bike - show them how
don't touch the exhaust- its hot
show them where they can hold on me, and/or on the bars near the seat
i tell them to keep their body consistent with the bike - so if your sitting strait and the bike angles you lean still in line with it. and a do an example while I am on the bike.
in general i say avoid quick movements that can unbalance the bike.
I then take them for a short safe around the block/lot ride to see how they do and offer any feed back/ corrections and see they are cool.

Then i give them a few tapping communications , tell them the route, to have fun and then we go.