Heart Piece #1 – Black Tower Entrance (Past)
Once you obtain the Shovel from a construction worker, exit the Black Tower and go one screen south. There you’ll find a Piece of Heart blocked by patches of dirt. Dig them away by using your newfound shovel to nab a very easy Heart Piece.
Heart Piece #2 – Maku Road (Past)
After visiting the Maku Tree sprout in the past, enter the Maku Road and go west from there into another room. Defeat the Stalfos enemies and notice the Piece of Heart enclosed in the block arrangement. Push the lower-left block up and the lower-right block left in order to gain access to the Heart Piece.
Heart Piece #3 – Yoll Graveyard (Present)
Once you’ve obtained the Power Bracelet, go to the southwest part of Yoll Graveyard (two screens west of Spirit’s Grave), where you’ll obtain the Piece of Heart after lifting the heavy stones guarding it.
Heart Piece #4 – Deku Forest (Past)
From Wing Dungeon in the past, go west two screens, then south one. You’ll find a sapling that once burned with an Ember Seed, reveals a staircase. Go down into the cave, then proceed westward to reach a previously inaccessible Piece of Heart.
Heart Piece #5 – Talus Peaks (Past)
Take the west exit out of Lynna Village in the past, and once you dead-end in the west, proceed a couple screens northward and enter the cave. Inside, jump the gaps with Roc’s Feather and lift the jars with the Power Bracelet to reach a Piece of Heart in the corner.
Heart Piece #6 – Talus Peaks (Present)
Beginning in the ancient past at the house in Symmetry Village housing the Tuni Nut, go west, south, west, north, and finally west. Standing in the southwest corner, play the Tune of Currents to return to the present age. Now in the present, go east a screen to claim your Piece of Heart.
Heart Piece #7 – Lynna City (Present)
First, start in the past. Go to Lynna Village one screen north of the Ember Seed Tree. See the two trees jutting out horizontally? Stand immediately above them, as far left as you can while still being above the westernmost tree. Now use the Tune of Currents to warp to the present age. If you positioned yourself correctly, you’ll be in a narrow, fenced-in corridor. Now enter the secret entrance to the shop, and once inside proceed northward down the stairs. In the secret shop, you’ll find a Piece of Heart on sale for 500 Rupees.
Heart Piece #8 – Rolling Ridge (Present)
Go to the southwestern screen in present-day Rolling Ridge and enter the cave you see there (not the stairs but the doorway). Go up the stairs and follow the path around until you see a Goron. Use a Bomb to blow up the cracked wall near it, opening the way to a Piece of Heart.
Heart Piece #9 – Rolling Ridge (Present)
This one is located on the farthest northeast screen of the game–but is tricky to get. First, clear Crown Dungeon. Afterward, from the dungeon, go east once and enter the cave, following it until its end. When you emerge, go east, north, and then east again. Play the Tune of Ages near the cave entrance to go to the past. Now you’ll be able to access the corner of the map. Slash the bushes, and in the corner, play the Tune of Ages again to return to the present, now able to collect the Piece of Heart.
Heart Piece #10 – Crescent Island (Present)
With the Mermaid Suit in hand, enter the deep waters on the northern coast of Crescent Island and dive underwater. In the northeast part of the island, you’ll find the entrance to an underwater maze beneath Crescent Island. Begin by going south until you can go no farther, then proceed westward. When the road forks off to the south, swim south and continue until around the bend until you’ve gone as far west as you can. From there it’s just a straight shot north (but watch out for the whirlpools) all the way to a cave entrance. Inside the cave is a Piece of Heart.
Heart Piece #11 – Maple
Unfortunately, this Piece of Heart is found completely at random. Whenever you bump into Maple, she drops a good many treasures, most of them of little worth. On very rare occasions, however, she’ll drop a Piece of Heart. When she does, be sure to pick it up, and quickly! You don’t want to have to repeat this sequence again and again, so grab it when she drops it. To increase Maple appearances, wear Maple’s Ring. And believe it or not, despite the time paradox, Maple makes appearances in Labrynna’s past as well.
Heart Piece #12 – Gasha Nut
Unfortunately, this Piece of Heart is found completely at random. By planting Gasha Seeds in soft soil, over time they grow into a full-blown Gasha Tree, letting you cut open a Gasha Nut to take whatever is inside. Gasha Nuts will give a variety of items. On rare occasions, though, you’ll even 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. Also, you tend to have more success by planting in soft soil locations that are harder to find and/or reach.