Ocarina of Time: Trading Sequence
Before you begin this sidequest, there are a few things you must do. First, you will need to be Adult Link. No part of the trading sequence is done as a child. Next, you will need Epona, as you will be transporting some items that will expire after a time limit. You will also need to unfreeze King Zora using blue fire.

While no part of the sequence is done as a child, there are two things you can do as a child to prepare for the quest. The first is to learn the Sun's Song, as you will have to wait for extended times at two parts in this quest. The second is to plant a magic bean seed at the entrance of Dodongo's Cavern, as you will be racing up Death Mountain near the end of this quest.

Finally, keep in mind that during sections where you must race against a time limit, you must not use any warp songs. This will bring the timer to zero and you will have to start that section of the quest over.

1 - Pocket Egg
To begin the trading sequence side-quest, go to Kakariko Village and speak with the Cucco Lady. After your conversation, you will recive a pocket egg. Now either wait, or simply play the Sun's Song until the morning of the next day, and the egg will hatch into a Pocket Cucco. Now go to the house to the right of the potion shop, and use the Pocket Cucco while standing next to Talon (who is sleeping on a bed) and wake him up. After your conversation with him, return to the Cucco Lady and give her the Pocket Cucco, who is now happy having woken up Talon. After your conversation, the Cucco Lady will give you Cojiro, a blue cucco who has not crowed since the Cucco Lady's brother left home.

2 - Cojiro
Go to the Lost Woods to the area where Skull Kid normally is (the area to the immediate left of the entrance). You will find a man sitting on the ground (he is the Cucco Lady's brother). Walk up to him and show him Cojiro, who will promptly crow upon seeing the brother. He will give you a mushroom and ask you to quickly take it to the Old Hag in Kakariko Village.

3 - Odd Mushroom
The mushroom will go bad in three minutes, so call Epona to cross Hyrule Field within the time limit. After you deliver the mushroom to the Old Hag, she will give you a potion to take back to the man in the forest.

4 - Odd Potion
When you return to the Lost Woods, you will find that the man is gone. A girl will inform you that he has turned into a Stalfos, and will give you a saw that the man dropped.

5 - Poacher's Saw
Take the Poacher's Saw to the carpenter crew leader that is standing outside the tent in Gerudo Valley. You will need either Epona or the Longshot to get across the broken bridge (or you can simply cross the bridge if you have already finished that part of the game). In exchange for the saw, the carpenter will give you a broken Goron Sword.

6 - Broken Biggoron's Sword
Now, go to the top of Death Mountain and show the broken sword to Biggoron. He will explain that before he can repair the sword, he will need eye drops, because his eyes have become filled with ash from the volcano and he can not see. He will give you an eye drop prescription to take to King Zora.

7 - Prescription
You will need to unfreeze King Zora with blue fire if you have not already. After you give the prescription to King Zora, he will tell you that he needs to get the eye drops made first. He will give you an eyeball frog to take to the scientist at Lake Hylia.

8 - Eyeball Frog
Like the mushroom, the frog has a three minute time limit before it expires, so you should use Epona to get to Lake Hylia. Once you deliver the frog to the scientist, he will make and give you the eye drops to take to Biggoron.

9 - World's Finest Eye Drops
Unlike the other perishable items, the eye drops have a four minute time limit, but you will still need to use those minutes wisely. Once you reach Death Mountain Trail, you can use the hover plant if you planted a magic bean as a child. If not, simply run as fast as you can up the mountain and deliver the eye drops to Biggoron. After applying the eye drops, he will give you a claim check for Biggoron's Sword, telling you to come back in three days, after which he will be done repairing the sword.

10 - Claim Check
If you have learned it, simply play the Sun's Song until the three days have passed, or you can wait the three days and return to Biggoron when he is done. Show him the claim check, and he will give you the grand prize of the trading sequence, the Biggoron's Sword.