INFERNAL DINOSAUR: KING DODONGO-
Difficulty Rating: 2
Boss of Dodongo's Cavern, King Dodongo is pretty easy. Just throw bombs in his mouth when he opens it to breathe fire at you and then hit him with your sword. Repeat until he dies.

BIO-ELECTRIC ANEMONE: BARINADE-
Difficulty Rating: 2
Boss of Jabu Jabu's belly, Barinade's not very hard. All you have to do is Z-target onto a certain part of its body and throw boomerangs. Then, kill the jellyfish that armor him. Repeat until he dies.

EVIL SPIRIT FROM BEYOND: PHANTOM GANON-
Difficulty Rating: 4
Boss of the Forest Temple, Phantom Ganon is pretty hard. First of all, he will ride on his horse and jump out of the pictures. If he creates a purple portal, fire an arrow at him. If he doesn't, then that was just his duplicate and you are doomed (unless you brought fairies). After doing that three times, he will get off his horse and float around. When he fires at you, hit it with your Master Sword so that it bounces back and hits him (watch out, because sometimes he blocks it right back at you). When he collapses, hit him with your sword. Repeat until he dies.

SUBTERRANEAN LAVA DRAGON: VOLVAGIA-
Difficulty Rating: 4
Boss of the Fire Temple, Volvagia is a pain in the neck. Wait till he sticks his head out of one of the holes and hit him with your hammer. Then with your sword. Watch out. When you hit him, he will fly around the room dropping rocks or fireballs on you. Repeat until he dies.

I haven't made it any further than Fire Temple yet so this FAQ will remain incomplete until I beat the game. Sorry!