The trading sequence in Ocarina Of Time is a little tricky to work out, but worth following through. As a reward for completing the quest, you receive Biggoron’s Sword, the biggest sword in the game.
Go to Kakariko Village as Adult Link, and talk to Anju (the Cucco Lady). She’ll ask you to look after a Pocket Egg, so keep it until it hatches (this takes a couple of night/day cycles in-game). Once it hatches, see Talon in one of the houses in the village and show him the Cucco. The Cucco will crow, and Talon will wake up quite confused. Take the Cucco back to Anju and in return you’ll get a blue Cucco, called Cojiro.
Anju will ask you to take Cojiro to her brother in the Lost Woods. Enter the Lost Woods and take the first left. He’s there, under the tree stump the Skull Kid perched on as a child. Show him Cojiro and he’ll cheer up, giving you a Mushroom in goodwill.
Give the woman in the Kakariko Village Potion Shop the Mushroom. She’ll make a potion out of it to give to the man in the Lost Woods.
Go back to where Anju’s brother was. He’s not there any more, but there is a Kokiri girl, to whom you give the potion. In return you get the Poacher’s Saw.
Now head off to Gerudo Valley, where the Carpenters are. Speak to the man in charge - the rather jolly looking fat man standing outside the camp - and give him the Saw. For your troubles you receive a broken Goron Sword. You are told to go to Goron City to get it fixed, so off you trot…
Climb your way to the top of Death Mountain, but instead of going into the Crater, run up the path to the right. Biggoron will appear, and says he would fix your sword for you if only he could see. He’ll give you a prescription to take to King Zora.
Give the prescription to King Zora in Zora’s Domain, who will give you the Eyeball Frog. You only have three minutes before the frog dies, so move fast using Epona.
Go to the Lakeside Laboratory in Lake Hylia with your Frog, and give it to the professor in there. He’ll produce some Eye Drops if you go there in time, which you are to take back to Biggoron, but within four minutes. Don’t warp, but use Epona to get there quickly.
Biggoron will be very thankful for you bringing him the eye drops, and will give you a Claim Check that you can use to claim your sword in a few days. Use the Sun’s Song to make that time pass quicker, and come back to collect it.