Automatic health restoration:
When your health gauge is low, visit a lake of a Great Fairy to restore your life. When you approach the lake, your health will slowly fill. While your health is being restored, press start to enter the item selection subscreen, and your health will continue to fill. Using a controller in port 2, press Up + A to return to the save menu. Select SAVE, and load your character's file. Once loaded, instead of remaining at the default of 3 filled heart containers, Link will have his health fully restored at the start.
Entrance to the Second Quest:
At the name entry screen enter: Zelda.
Fewer enemies:
Kill all the enemies except for one in a particular screen, and next time you go through there will only be that one enemy there, instead of them all coming back.
How to bring up The Secret Save Screen:
For this code you need Two Controllers. On controller 1 Press start. On controller 2 Press Up and A at the same time. This will bring up The Secret Save Menu. So now you don't have to die to save.
Kill Gohma easily:
Before entering Gohma's room, ready the bow and arrows. Now go inside and quickly shoot an arrow. Gohma will be exactly in front of you with his eye open so he will die in one shot.
Magically Unlock A Door:
As soon as you enter Level 1, exit. Then, go back into Level 1. You will notice that the northern door is now unlocked.
Refill Red Water of Life:
If you bought a red-colored Water of Life, when you use it once, it turns blue, meaning you can only use it once more before it disappears. To refill it from blue to red without buying a second Red Water of Life from the Old Woman, buy a Blue Water of Life. Doing so will make it red again.
Undo The Bubble Curse Instantly:
If you're touched by a flashing bubble, instead of waiting for its curse to wear off, immediately blow the whistle. The moment you stop playing, you'll have the ability to use your sword again. (NOTE: This trick doesn't work against the red bubbles in the second quest.)