Maps for the DM.
Handouts for the players, with a DM marked version for anything special the players shouldnt see, but need to be denoted.
Well playtested adventure/scenario.
Plot related NPCs as opposed to generic ones.
Background info on places and NPCs enough in case the players go off the beaten track a little to guide the DM in direction to know what the NPCs would be doing if not standing around waiting for the PCs to meet them in Room 11a of the "dungeon". These motives and such could be in an Appendix to be read and understood before running.
Story that gives reason to play it.
Ability to plug into any game, while still allowing for the module to continue in a series if wanted.
Pre-gened character so you can just play right away if you don't want to take the time making them.
Tokens or fold-ups that can be photocopied/printed to have the correct representations needed for any combat situation where a physical representation is needed for some players. Properly named, not just images, for those needing names. Also becomes a good reference when meeting an NPC to speed up describing what the PCs see since they can see this character as the players.
Good organization. If printed, then goblins shouldn't be in the back of the book to flip back and forth but simple enough to print/photocopy to be found without flipping back and forth to the location they are in, or removed form the printed copy easily.
-KotS was in a folder I think, so the folder could have one side the adventure, and the other the resources for it like handouts, maps, pregens, monster sheets, tokens/fold-ups, etc.
Index/KEY maps not only offer room numbers for the DM to find Room 11a, but a page number to take them directly to it.