Yoshi Doll - The Yoshi Doll is found in Mabe Village. All you have to do is play the Trendy Game. Since the Yoshi Doll doesn't move, it's fairly easy to grab. Once you have it, go to the Quadruplets' Home (also in Mabe Village), and give the doll to the mother.
Ribbon - When you get the ribbon, go to Madame MeowMeow's house (a few screens southwest), and trade it to her for the dog food.
Dog Food - Take the dog food south to Tornobo Shores, near where Link was found. There is a lone house there, and inside, Sale is willing to trade you the dog food for some bananas.
Bananas - You'll have to take these bananas to Kiki, the monkey just outside Kanalet Castle.
Stick - It may seem odd, but someone actually wants a stick, which you'll get from Kiki. Take it to the northeast part of Ukuku Prairie where you'll find a lone tree with a honeycomb in it. You'll also find Tarin, who will poke the beehive with the stick once you give it to him. After the bees chase him away, you can take the honeycomb.
Honeycomb - Take the honeycomb to Animal Village. More specifically, take it to Chef Bear's house. You will get a pineapple for your efforts.
Pineapple - With the pineapple in hand, go to Tal Tal Heights. Along the way to Angler's Tunnel, there is a screen with a waterfall and three caverns above it. Before that is a screen with a lone cavern in the mountain wall. Enter the lone cavern, and when you come out, look for Papahl. He is stranded and too tired to move on, but the pineapple will get him going again.
Hibiscus - Go all the way back to Animal Village and offer Christine the Hibiscus. She'll give you a letter.
Letter - ...And who better to give a letter to that Mr. Write? His house is just north of the Mysterious Forest. He'll give you a broom, because he's so happy that someone finally gave him a letter.
Broom - Go to Mabe Village, and look for Grandma Ulrira. She'll gladly trade the broom for a fish hook.
Fish Hook - At the southeast part of Martha's Bay, there is a bridge that crosses above some rocks. Take the fish hook here, and dive under the bridge. You'll find a man fishing here. He agrees to give you the next thing he catches, and that just happens to be a necklace.
Necklace - Take the necklace to the mermaid just north of Catfish's Maw. She'll be so happy that she'll let you take a scale from her tail (but only one).
Scale - Take the scale to the mermaid sculpture just south of Catfish's Maw. It's the missing piece of the sculpture. Once inserted, the sculpture will move to the side, revealing a hidden staircase.
Magnifying Glass - The final item to trade... or is it? Well, not really, because you can't trade it. But you can trade something else. Now that you can "see the truth", go back to Tornobo Shores. Walking along, you'll notice a wall with a crack in it. Blow it up, and go inside. The creature inside will trade you anything for the boomerang. My suggestion is the shovel, but make sure you've got all the seashells you want with it first. It's definately worth the trade, because the boomerang is very powerful, can travel far distances while you move around the screen (not like the hookshot), and can collect items for you that are out of your reach.