You should explain the rules of riding pillion before rolling, I know. But that's not always easy to do when you have a girl, who you want to impress, and you don't want to come off as a anal-retentive weiner. I just take it easy the first few times on the road with that person, and she eventually picks up the etiquette.
At the very least, you should tell the passenger about the exhaust pipes and the wheel and drivechain, to not get on or off without letting you know beforehand, and if it's a guy, to lean as you do - this usually happens normally with girls, since they're more willing to grab your waist while riding.
--2000 VTR1000F Super Hawk