The rule against perpetuities.
It's a bitch.
Yes, I studied it in law school, but I don't remember it being this complicated! Certainly I never had to learn anything about vested interests or contingent springing defasible options subject to open executory interests or any of that crap.
Now, I know I'm not stupid, I deal with all kinds of complicated crap at work all day, every day, but somehow I just cannot get all these stupid interests in my head.
I suspect that my preparation tactic in this respect will be to just memorise everything and not even bother trying to understand it, since that currently seems like a totally pointless exercise...