Getting on and off...
One thing I forgot to mention - tell the old lady to grab hold of _you_, instead of the bike, to lever herself on and off. One thing inexperienced passengers are terrible about, is thinking they're getting on a bus or something and yanking the bar to hoist themselves on-board.
That can pull the unwary biker horizontal, or at least give them the most unpleasant experience in avoiding it. And then the tart who's just nearly pulled you both off rolls her eyes and wonders what your problem is.
But - ehem - we're talking about the misses. If she grabs _you_ instead of the bike to haul herself onboard, things will run much more smoothly. Same with getting off. She's not going to treat _you_ like a piece of railing, hopefully, and you'll be able to react and counter the forces.
Taking mates for a spin can be amazing, if they are good bikers myself. Adding my mate Jamie to the passenger manifest seems positively odd - I sometimes have to look behind to make sure he's still there. He's so good, you can't tell he's there at all.
Another amazing thing about such a good pillion rider, I was still waiting for him to get on when he gives me two slaps on the shoulder to confirm he's ready to take off. Didn't even notice the bastard get on or off the back. He's that good.