I think I've touched on this before, but Stuart brings up a good point in the comments to my last post. I'm not going to address that directly, but instead look at something tangential. Specifically, how do you create meaningful choice in the dungeon?
It can be difficult. Players assume certain things between staying on a certain level or going deeper. (Whether or not they should is another matter entirely.) Beyond that, typically the passage east is pretty much identical to the passage west. There's typically little reason to choose one over the other.
How to fix that? Generally, folks will tell you to hit the other senses: are there smells, or hot drafts of air, or sounds one way or the other? More to the point, however, is what you might be trying to communicate by these clues. What, beyond the inhabitants, is there that makes one part of the dungeon different from another?
When I'm sitting down to beat on a dungeon, I try to break the place up into zones. Typically, these zones are based on what the original builders had in mind for the location. The passage to the left has ornamental carvings on the arched doorway, while the passage to the right is narrower and without ornamentation. The left leads to the living quarters of the owners of the place, while the passage on the right was an access hallway for the servants. That sort of thing gives players all sorts of information to play with. To the left, the hallways will be broader, the rooms bigger. That's where the best treasure and bigger monsters are likely to be found still. The narrower hallways and smaller rooms of servants' territory, however, probably go everywhere and might provide ways to get around things and creatures best avoided, or offer tactical possibilities.
Just like your home is divided into zones, so too can you divide your dungeon. Your home probably has a kitchen and dining area, a sleeping area, and a working and living area. You might have nice rooms that you don't use unless you have company coming over, and you might have a workshop that you're in a lot but company doesn't visit much. The critters living in your dungeons have the same needs and interests. Where do they sleep? Where do they work? Where do they get their drinking water and where do they get their food? They also have other issues to keep in mind. How do they protect themselves against the bigger, nastier critters that live deeper down in the dungeon? These sorts of things might map directly on to the intentions of the original builders, or may have been altered by the new inhabitants. What was a bedroom is now a storeroom. The great hall is now a barracks. Regardless, this new habitation is going to leave clues. Kitchens and latrines broadcast odors that sharp-nosed adventurers might sniff out. Smithies will make lots of noise, as will makeshift taverns or barracks or dining halls, kennels, and nurseries. The most "important" rooms will be guarded. Vaults where loot is stored might be guarded with monsters, traps, or both. The locations where slaves are kept will likely be cruder and less well-maintained.
Finally, don't hesitate to give your players opportunities for reconaissance, either via rumors before they enter the dungeon, or from captives or spells once they are inside. The essence of all games is making meaningful choices; the more information the players have, the more fun they can have doing things with the neat dungeon-toy you've given them to play with.
Art by Jean-Léon Gérôme.