World and lore
Work out when a place is open, including nights that cross midnight
The tavern opens at eight in the evening and closes at two, and your game says it is shut at one in the morning. Here is the small rule for opening hours that run past midnight, closed days and the answer to "how long until it opens".
Let the world act during a night's sleep, and wake the player if it must
When the player rests until morning, a market opens, rain starts and a burglar climbs through the window, and skipping the hours must not skip these. Here is how to run the skipped time event by event, in order, with sleep that can be broken off.
Pick a start spot near water and away from danger, and say why none fits
The new world drops the player by a pond full of wolves, or two days from any water, and the story has barely begun. Here is how to rule out the unplayable spots first, then rank the rest, and how to get a clear count of what ruled spots out when the world has no good start.
Let a storm front sweep over the regions without skipping any
A storm that moves across the land should hit every region on its way, but a game that looks at the weather once a day lets a fast storm jump clean over a small valley. Here is the way to ask which regions were really under the storm during a day.
Move a story place the player has flattened to the nearest spot they can reach
The hermit's hut was meant to stand on the hill, and the player dug the hill away or built a fortress on it. Here is how to find the closest spot where the hut can still appear, one the player can actually walk to, instead of one that looks near on the map but lies across water.
Make a shadow clue that tells the hour and still works in winter
A riddle says to dig where the stone's shadow points at midday, and the player, who plays through a winter, finds nothing at the appointed hour. Here is how to compute where a shadow points and how long it is for any hour, and how to turn a shadow back into the hour, with short winter days.
Open a sea cave only at low tide, with times that move from day to day
If the cave opens at six every morning, the sea feels like a door with a timer and not like the sea. Here is how to give the tide a real rhythm that slips later each day, list the windows in which the way in is dry, and tell the player when to come back.
Check that the torches in the pack last through the dark parts
A dungeon with a long dark tunnel, a lit bridge and a dark crypt asks the player to ration light, and a map that cannot be crossed with the torches on offer is a trap nobody meant. Here is a walk through the route that says where the light goes out.
Show a torn-up old letter with gaps for the pages still missing
The player finds the bottom of a letter first, then the top, then a scrap in the middle, and the text should read right at every stage. Here is how to join the found parts, mark each gap once, and tell when the whole thing can be read.
Turn a walking time into the words a local would use, never too optimistic
"Two days from here" for a trip of three hours, or "a short walk" for most of a day, and the player runs out of food or loses trust. Here is how to turn exact minutes into the vague phrases people really use, so that the phrase rounds the right way and stays close to the truth.
Check that stated travel times between places make sense together
Chapter one says the mountain pass takes five days and chapter six says the detour through the valley takes two, so nobody would ever use the pass. Here is a check on the whole map of distances that finds shortcuts that make a stated route silly.
Check that a treasure riddle with two compass lines has one findable answer
Walk from the tower on this heading and from the rock on that one, and the treasure lies where the lines meet. Here is how to calculate the meeting point, and to catch the riddles where the lines never meet, meet behind you, or cross at such a shallow angle that the spot is a guess.