Note that this glitch requires the use of a NES controller that allows Left and Right on the D-Pad to be pressed at the same time. By pressing Left and Right at the same time, there is a glitch in the game's programming which allows Link to move with much higher velocity than normal, so high such that he can often enter and go through walls. You can alter your speed and direction by changing your facing or tapping Left or Right on the D-Pad while the other is held.
To avoid forced battles (battles by stepping on a certain tile on the field) simply wait in front of it until monsters appear and when one steps on the tile, move onto the tile and you'll go into a battle scene from the monster, not the tile. Most monster battle scenes are much easier than the tile's. Extremely useful when going to the Great Palace.
To quickly earn more experience for a new character, first have a character who is far along in the game but hasn't done all the palaces yet. Have this character beat a palace and go to the place to insert the gem.
When you insert the gem and the experience points start to total up, pause and do the Quick Save. Then, load your new character. All of the experience points which would've gone to the character you beat the palace with will now go to your new character.
If you come to a locked door and hove no key you can simply use the Fairy spell and fly right throuogh the keyhole. And sometimes if you have enough magic you can make it through the whole palace just using this trick.
Make sure you have two controllers in. Now on controller 1 pause the game, on controller 2 press up and A at the same time. You will be taken to a menu where you can save or continue.