The First Quest
The first mission is to rescue Zelda from the castle dungeon and bring her to the sanctuary. Once Zelda is there, you can begin the quest to find the three pendants and get the Master Sword to fight Agahnim.
The Pendants
The Pendant of Courage can be found in the Eastern Palace, the Pendant of Power is in the southwestern desert, and the Pendant of Wisdom is in the tower atop Death Mountain. Once you have all three, you can get the Master Sword in the Lost Woods.
Battling Agahnim
Once you have the Master Sword, it's time to return to the Castle to face Agahnim. You must use the Master Sword to reflect Agahnim's own spells back at him.
The Seven Maidens
You will reach the Dark World after beating Agahnim. Here, seven maidens are held prisoner and scattered throughout the land. You must travel back and forth between both worlds to find and rescue all seven maidens.
Items
There are several items you must find throughout both worlds. These include Heart Container pieces, upgrades to your sword, shield, clothing and arrows, a flute, magic medallions, multiple Dark Gates and the ability to carry more bombs and arrows.
Ganon's Tower
With all seven maidens rescued, you head for Ganon's Tower on the Dark World's Death Mountain. You must make it up the tower and face many of your old enemies before facing your final foe, Ganon.