When I used to appear in court a lot, I ran into plenty of intelligent people who managed to mess up badly because they didn't follow simple, clearly advertised

When I used to appear in court a lot, I ran into plenty of intelligent people who managed to mess up badly because they didn't follow simple, clearly advertised, rules. So even though in theory it should be simple to do something, in practice people often get it wrong. i.e. even where it isn't opaque, it is surprising how many people mess up. (Of course that includes lawyers)