Instructions
Enter Death Mountain after crossing Lake Hylia. The sign posted in front of the cave entrance to Death Mountain tells Link that he needs the king's permission to enter. Ignore the sign and enter the cave.
Talk to the lost man inside the cave. He'll follow you as you navigate the cave. Watch out for holes in the ground.
Avoid falling rocks as you exit the cave onto a higher plane of Death Mountain. To the right there is another cave entrance. Go in.
Talk to the man again inside the cave. He will refill your hearts and tell you about the Moon Pearl, a necessary part of the quest. Head up and to the right, and go through the doorway. Follow the new pathway down and to the right, and go through the doorway. In the last cave passage, walk down and to the right to exit the caves back onto the outside portion of Death Mountain.
Run to the left and up, towards the ladder. Avoid the falling boulders. To the left of the ladder is a cave entrance that takes Link off the mountain; keep that in mind if you run into trouble or don't have a necessary item later in the game.
Climb the ladder and head to the right. Past the cave entrance is a blue square -- this is the warp portal. Stand on it, and Link will be transported to the Dark World, where he is transformed into a bunny. Talk to the weird creatures, who will tell Link more about the Moon Pearl.
Use the mirror the old man gave you to leave the Dark World Death Mountain.