Heart Piece #1 – Horon Village
This is probably the first Heart Piece you can collect in the game. Once you have Ember Seeds, go to Horon Village, one screen north of Vasu’s ring shop. There you’ll find a sapling. Burn it and claim the Piece of Heart that it was guarding.
Heart Piece #2 – Eastern Suburbs
Once you’ve gained the power of winter in your Rod of Sesaons, go to the tree stump two screens east of the exit out of Horon Village. Turn the season into winter and go one screen north. Cross the bridge made by the snow bank and enter the cave you find to the west underneath Guru Guru. Inside you’ll find the Piece of Heart.
Heart Piece #3 – Woods of Winter
In the far southeastern corner of the Woods of Winter lies another Piece of Heart. To obtain it, use the Rod of Seasons to transform the environment to winter. Now walk across the icy pond and use the Power Bracelet to lift the rock blocking your way and claim the Heart Piece. Alternatively, you can use Zora’s Flippers to swim across the pond and not worry about the season or the rock.
Heart Piece #4 – Subrosia Market
Once you are able to reach this Subrosian shop (in the southern part of Subrosia but north of the lava seaside), you can purchase a Piece of Heart for 20 Ore Chunks and 10 Ember Seeds. A very good deal indeed!
Heart Piece #5 – Eyeglass Lake
Go to the tree stump either where you met Din at the beginning of the game or the one a single screen to the west (on the way to Unicorn’s Cave) and summon summer. The lake a couple screens to the southeast will be dried up now. Walk along the bottom of the dried lake and lift the stone to uncover stairs leading down into a cave. Inside, follow the staircases and avoid enemies and obstacles, and you’ll soon find the Piece of Heart.
Heart Piece #6 – Moblin’s Keep
Brave the Great Moblin’s stronghold west of Sunken City and defeat the king of the Moblins by throwing his bombs back at him. For the final blow, you must throw a bomb such that it explodes when he is holding a bomb, which will cause all the bombs behind him to detonate, thus bringing the entire stronghold down. When the Moblin’s Keep is destroyed and the Great Moblin has fled, he leaves in his wake a treasure chest containing a Piece of Heart.
Heart Piece #7 – Spool Swamp
If you go to the southeastern section of Spool Swamp, you’ll notice a Piece of Heart lying on an island, yet it’s surrounded by insurmountable vines. How to reach it? Go to the tree stump a few screens to the north and change the season to spring. Now return southward to find that the vines have been replaced by a rapid current, encircling the Heart Piece. Dive in with Zora’s Flippers and do your best to navigate the current, aiming to land on the island with the Piece of Heart.
Heart Piece #8 – Mt. Cucco
Find the tree stump that’s at Mt. Cucco and turn the season to spring. Then make your way a couple screens westward and use the flower to reach the higher ledge above. From there, go back eastward to the entrance of Dancing Dragon Dungeon and drop down from there to the ledge to collect the Piece of Heart that’s out in plain view.
Heart Piece #9 – Graveyard
You will need Roc’s Cape first. Once you have it, use the piratian ship on the Western Coast to reach the other side and an abandoned house (one screen north of the ship). Traverse the house to the other side where you’ll find a tree stump in the fenced in yard. Turn the season to autumn. Now enter the cave west of the ship and use Roc’s Cape to soar across the large gap. When you exit the cave, you’ll find yourself in the Graveyard. Go northwest (where the entrance to Explorer’s Crypt is), pull up the mushrooms with the Power Bracelet, and make your way east to the waiting Piece of Heart.
Heart Piece #10 – Temple Remains
After you have been to Subrosia to cause fire to fall and lava to overflow the Temple Remains area, return to those remains. There will be a place in the north wall where you can plant a Bomb to open an entrance–look for the telltale cracked wall. Use Roc’s Cape to leap across the pits of lava and reach a Piece of Heart.
Heart Piece #11 – Maple
Unfortunately, this Piece of Heart is completely randomized. Whenever you bump into Maple, she drops a variety of items. On very rare occasions, she’ll drop a Piece of Heart. When she does, be sure to pick it up quick–make it your first priority! You don’t want to have to keep bumping in to her again and again, so scoop up when she drops it. To increase Maple appearances, wear Maple’s Ring.
Heart Piece #12 – Gasha Nut
Unfortunately, this Piece of Heart is completely randomized. By planting Gasha Seeds in soft soil, over time those seeds grow into a full-blown Gasha Tree, letting you cut open a Gasha Nut to take its contents inside. Gasha Nuts will give a variety of items. On rare occasions, though, you will find a Piece of Heart inside. In order to increase your chances of landing a better item from a Gasha Nut (and thus maybe a Heart Piece), kill lots of enemies, help townsfolk, advance the game plot, complete dungeons, and so forth. Don’t be too hasty to cut down Gasha Trees just as soon as they grow up!