As folks are surmising, there are multiple aspects to Pacing.
Pacing in combat can mean making it run faster and smoother (less dithering).
Pacing in dungeon crawling can mean hand-waving the room searches, and empty rooms.
For a low-level party of first time players, making decisions on watch order, making camp, opening doors, searching rooms might be novel and educational. However, it can get tedious. And for experienced players, they already know all this anyway.
Its not fun anymore, except for GMs looking for an edge to introduce a threat that exploits a mistake.
If you were producing the game as you would a film, what scenes would you leave off as boring, and extraneous to the story? There are some folks who can't let go of any of them, but all the good directors know there's a lot of material you can do without.
Its not about giving players a "Win" button, but cutting out the parts that make the game suck. If the players are on the wrong track for a missing boy, either move the boy to where they are, or bring in new information. Not because you want to hand them victory, but for the sake of having a good time and stopping the slow drag.
My overall tips are:
ask the players if they have an standard procedures for making camp, searching rooms and doors. If they don't, they'll lie and make one up. That's fine. Assume the follow this and aren't doing anything blatantly dumb. Now you can skip asking, and them declaring this kind of stuff.
Roll-up secret room checks in the dungeon in advance (use the best stat in the party if need be). Now simply declare when such things are reached and encountered.
Do the same for traps (you may need to devise a fair means of determining who set off the trap when a search is failed). Consider that failure means somebody in the party set it off and is now making a Save to avoid it as part of discovery. This removes tedious hallway and room searching, as it is implied. Special traps (like the one under the idol they are sent to retrieve) would not be handled this way, just the generic room and hallway traps.
In the beginning of the game, except for special items, let players buy items from the PH themselves, and sell items for 50%. Hand-wave this as "you all stop for supplies before heading out"
A realistic dungeon/cavern will be sparsely populated, namely lots of spaces will be unoccupied. hand-wave this exploration as "you explore and pass through many chambers, finding nothing, until..." wherein you introduce the setup for the next encounter. You won't have the false-positive setup of several rooms to lull the players into a trap, but you also won't bore them.
If you auto-assume the players are exploring until they encounter something, make sure you also incorporate decision points that matter in the dungeon. A hallway fork that has clues of danger about it. This changes up the encounter types (effectively, the fork is the encounter).
If the players over-plan in a dangerous area, have a "random" encounter ready to move into their area to sound an alert or trigger a reaction. Always have some kind of deadline threat that implies the players have a limited time to decide. You may not have to bring it in, and it need not be actually based on time. Just make sure at the start of their planning session, they are advised (possibly via NPC) that urgency is required in their planning by virtue of something will happen if they tary.
If the players are actively attempting to solve your game problem, but are going the "wrong" way, don't punish them by making the game drag out in fruitless effort. Either inform them in-game that this way is wrong, bring in a new clue to redirect them, or move the objective to where they players are going.
The game should still have fast paced moments (combat, chases, etc), as well as slower, more thoughtful scenes of discussion, decision making, and problem solving
For the GM who likes to introduce complications based on mistakes the players make (aka screw the players on micro decision making), those methods should probably be abandoned at the micro scale. Let the PCs be heroic, or whatever. Screw them over at the macro scale. Sure, the party always has good tactics for camping and crawling. But do they handle politics well? Do they consider who they ally with carefully? Do they pay attention to the impact of who they kill, and who they turn into the authorities? Do they question who they do business with?
These methods may be a huge shift for some in how the game is played. But they will likely be fun and challenging, and make bettter use of game time.