1. Think About Why

When creating a dungeon, the first question you must answer is: Why will your player characters risk going into this dangerous dungeon full of monsters and traps? Here are some possible scenarios: To Explore the Unknown: This is common in pulp fiction. One or more of the player characters has heard of some ancient site, and wishes to explore purely for knowledge. Possibly some of the other player characters are involved for other reasons. To Battle An Evil Incursion: Goblins are raiding farms in the area, and the Baron has offered a reward for stopping the raids; the player characters are happy to help. To Rescue A Kidnapped Victim: Some friend of the player characters has been kidnapped, and they must sneak into or storm the villain's tower/cave/dungeon to rescue the victim. Or, perhaps, the victim is the son or daughter of the local Baron or a wealthy merchant who offers a reward for the safe return of their offspring. To Fulfill A Quest: The local church, to whom the player characters owe a favor, would like an ancient relic recovered from a lost mountain fortress, and the High Priest asks them to look into it; or some similar task might be assigned, depending on who the player characters owe a favor. To Get Loot: This is a surprisingly common scenario (well, perhaps not so surprising). The dungeon is rumored to contain a hidden treasure of great value, and the first characters to find it will be rich! Of course, the treasure might not be that huge, and might be guarded by any number of horrific monsters… To Escape Confinement: The player characters have been captured by an enemy, and find themselves incarcerated without their weapons, armor, or equipment. This scenario must be used with care, as the GM must not be seen to be "railroading" the characters into the adventure. There are many other possible scenarios, and each has many variations. Knowing the answer to this question will make the next questions easier to answer.