Instructions
Defeat all of the monsters you find. This is the best way to get treasures such as rupees, hearts and bombs. Don't be defensive against the monsters--most should just be attacked head on.
Get all the items you can. Some are absolutely needed to win the game, and almost all others will be helpful at some point.
Look for secret caves everywhere. Bomb walls, burn trees and move statues to find them and see what they contain.
Listen to what people tell you in the game. They all have clues and information that will help you win.
Upgrade your sword as soon as possible. Get the White Sword once you have five Heart Containers and the Magic Sword when you have twelve.
Look for monsters' weak points, especially in the underworld labyrinths. Many are either weakest, or only vulnerable, to a certain type of weapon, and you just need to find out what that is.
Complete the underworld Labyrinths in order. Each one will be more difficult than the previous.