1. Mabe Village. Fall down the well from above. There’s a heart down here. You need the sword.
2. Mysterious Forest. Enter the log tunnel. If you have the power bracelet, move the stones to access the treasure chest.
3. Kanalet Castle. Once you get the flippers, swim all the way around the west side of the castle. In the very SW screen, dive near the bottom of the screen to find another Piece.
4. The Fishing Pond. If you catch all the fish in the fishing game, the last big lunker will have a Piece of Heart.
5. Ukuku Prairie. Use a Bomb to enter a secret cave, then use the Pegasus Boots to dash down the crystal blocks and find a bomb able wall. Bomb it and enter to find a heart.
6. Tal Tal Heights Water Cave. After finishing the Angler’s Cave, go right several screens until you see a cave. Go in it and dive underwater to find a Piece of Heart.
7. Eastern Tal Tal Mountains. Cross the rope bridge and whack down the bush. Now you can get to the Heart that you’ve seen for quite a while.
8. Koholint Prairie. You need Roc’s Feather to jump over the pits surrounding this one. It’s east of the Mysterious Forest.
9. Yarna Desert. After beating Lanmola, fall in the sand pit. Bomb the north wall to pick up another piece.
10. Animal Village. Take the path outside the eastern fence. Use the Hookshot to reach the heart piece.
11. Cemetery. Go to the Cemetery secret passage and push up the tombstone. You can use the Hookshot to get this one, or you can have Link jump diagonally across the pit.
12. Western Tal Tal Mountains. After exiting Turtle Rock through the back exit, you’ll see a heart in plain sight. Pick it up, already!