Instructions
Head to the Gamespot website Zelda page and check out their complete Ocarina of Time game guide. It has all the information you need to finish the game's main missions and extra quests. For a detailed and thorough walk-through, this is your best bet.
Cruise over to the IGN Ocarina of Time page for another game guide. Although one's usually enough to get the job done, having a second one handy gives you another reference in case you get lost or can't figure out one's instructions.
Read through the smaller cheats listed below the Gamespot game guide. These offer helpful hints on cutting corners in your overall quest. For example, you can learn how to acquire the Golden Scale as Young Link.
Browse through both sites' lists of in-game glitches. There are only a handful of these, but they can be really helpful. For example, one lets you stockpile as many as 24 bottles, which can get you through bothersome boss battles.
Look through the different user-created walk-throughs and Zelda strategy guides posted at the bottom of Gamespot's Ocarina of Time page. These often go into more detail than the official game guides and can help you tackle specific quests.