I've been searching for ages, but I only very rarely happen to find a dungeon. Does anyone know if there is a way to find dungeons that is 100% acurate?
Dungeons in Minecraft are randomly generated throughout the map/ground and the only way to find them without mods or third-party programs is to "keep digging", as Arperum posted.
EDIT - This only works near the surface of desert biomes, but you can find square depressions on the ground, caused by the sand falling into the space of the dungeon. Then you can just dig down.