Things You'll Need
Instructions
Finding Dungeons with Debug Mode
Press "F3" on your keyboard while playing Minecraft --- preferably while exploring a cavern system, as you're more likely to find a dungeon there. This brings up the game's debug mode as an overlay to the usual first-person perspective and displays numbers over every animal and monster in the game. These numbers can be seen at great distances and through solid blocks. Debug mode was added in Minecraft version 1.3_01, so you'll need that version or, preferably, a more recent version.
Look around for high concentrations of numbers moving about the screen. It's unlikely that these are animals if you're underground, so a large number of numbers is usually evidence of a dungeon.
Dig toward the numbers, but be careful not to accidentally dig into lava or an underground river. You'll still have to deal with the monsters once you arrive at the dungeon, so make certain you're carrying food and armor.
Press "F3" again to turn off the debug mode once you've found the dungeon.