Not only is B1 In Search of the Unknown probably the best introductory module for Dungeons & Dragons ever published, it is one of the very few D&D modules that also has extensive notes for the fledgling DM. The sections "Notes for the Dungeon Master", "Preparation for the Use of the Module", "Time", "Computing Experience", and "How to be an Effective Dungeon Master" are one of the best five page tutorials for running ANY edition of the game. Some of the advice is really good for any type of RPG, not just D&D.
"First, it is crucial to keep in mind that this is a game based on player interaction and player choice. The game generally follows the course of the player's actions—if not always their plans!"
"Although you may set up situations to challenge them, you must understand that you are not their adversary, nor are you necessarily out to "defeat" them"
"if your players abandon caution or make stupid mistakes, let
them pay the price—--but be fair."
Good advice for any beginning gamemaster!