I'd like to see weaknesses and such be procedurally generated, but unique to monster type. So all the hags are weak to oak wood, and the trolls hate honey, or whatever. Of course, right now I think that each individual night creature is unique compared to all the rest, so unless we get one super-successful night creature that takes enough mates and sires enough children to perpetuate itself (a la Dracula), then we have to deal with the odd fact that the peasants somehow know how to defeat the night creature, but are unable to do it themselves.
If monster types do end up being the way Toady goes (or the successful single night creature posited above), then you have the justification that some folk hero has killed one before, and therefore everyone knows the story. This leads to the situation where all the villagers just know that if you carry holly berries around on your person the local monster won't bother you- unfriendly little towns may withhold this information in order to dispose of unwelcome foreigners who wouldn't know the custom. This could lead to the quasi-symbiotic situation where the villagers are afforded some measure of protection from bandits and the like because the outsiders do not know how to defeat the monster, and since this is beneficial to the villagers they never tell outsiders how to defeat it, which helps the monster kill new victims.
Weaknesses may not kill the creature, though.
Vampires, as Dante was saying, have a weakness to beans - they aren't
killed by beans, but they have to stop and count the beans. It distracts them.
I've looked up mythologies from around the world, and some cultures have very quirky, if not outright humorous "weaknesses" for some monsters.
Kappa, for example, are Japanese river creatures that look like humanoid turtles with beaks and carry a plate on their head. The plate is somehow affixed to the top of their bald head and contains the water from their home body of water. If they ever lose contact with their home water, they die immediately, so breaking the plate is the killer weakness of the creature. Their second-favorite meal is human (especially human children)... something. The actual thing they eat changes depending on the story, but generally, it's either the livers, intestines, or some portion of the human's soul, which they suck out through the belly button (or some other, lower opening in the human).
Thing is, their absolute
favorite food is cucumbers. So if you bribe kappa with cucumbers, they'll leave you alone, and won't eat you. There are festivals where people write the names of their family members on cucumbers, and toss the cucumbers in the river to bribe the kappa every year, giving up a tribute of cucumbers so the monsters don't eat their souls.
Other amusing things are that, for all their potential soul-eating, you can just plain talk to them, as well, and they were forced to obey customary politeness. If you bow deeply to a kappa in greeting, they would have to bow just as deeply in return, which could spill the water out of their plate, and defeat the kappa for you.
Anyway, something like a way to distract or bribe a monster would probably be more generally known knowledge, since it's something where you didn't have to kill the creature to know it. Maybe a not-quite-so-hostile monster will just outright go up and
ask to be bribed if he prefers people throw him his favorite food of their own accord as a sort of protection racket. I mean, the more people know that leaving your favorite whip wine out near your cave will keep you from busting in and killing their family, the more whip wine you'll suddenly find out near your cave for you to drink whenever, right?