The following is a list of all of the Pieces of Heart in Ocarina of Time, with a description of how to get each one, and whether you need to be a child or adult to get it, and whether you need to get it during the day or at night.

List of Pieces of Heart

1. (Child/Night) Hyrule Castle Town - At night, find the white dog by the empty stall in the corner of the market near the entrance to town, and walk up to it to get it to follow you. Take it to the back alley and show it to the woman in one of the houses to get a piece of heart.
2. (Child/Day or Night) Lon Lon Ranch - In the silo, pull the crate away from the corner of the wall and crawl through the hole for a piece of heart.
3. (Child/Day or Night) Lost Woods - Play the song game three times with the two Skull Kids after taking the first right in the Lost Woods.
4. (Child/Day or Night) Lost Woods - After learning Saria's Song, return to the Lost Woods entrance and take a left to find a skull kid on a stump. Play Saria's Song on the short stump and the kid gives you a piece of heart.
5. (Adult or Child/Night) Kakariko Graveyard - Get behind the last row of graves in the graveyard and look at the left-hand group. Pull back the grave second from the right. Inside, play Sun's Song to freeze the ReDead and kill it, then stand on the platform and play Sun's Song again to reveal a chest containing a piece of heart.
6. (Child/Night) Kakariko Graveyard - Play Dampé's Heart-Pounding Gravedigging tour. Make sure that he is standing on the edge of a dirt pile when you ask him to dig. Don't ask him to dig the same spot twice in a row; wait for him to go all the way around before asking him to dig at that spot again. The longer you play, the more likely it becomes that he will dig up the piece of heart.
7. (Child/Day or Night) Goron Village - Light the torches on the bottom floor of the Goron Village with fire taken from Darunia's room. The Goron Jar will open and start to spin. Pick a nearby bomb flower and throw it into the jar when it is near the ledge. If it stops with the happy face facing the camera, a piece of heart and 25 rupees will pop out.
8. (Adult or Child/Day or Night) Death Mountain Trail - There is a piece of heart above the entrance to Dodongo's Cavern. You can reach it as a child by going to the bomb flower that you can throw at the Dodongo's Cavern entrance to break it open. Throw the bomb flower somewhere, then stand with your back facing the short piece of fence, but turn slightly to the right. Then hold Z (or L in Ocarina 3D), then do a backflip to land on the ground above the cavern entrance. You get hurt, but the piece of heart here replenishes your health. As an adult, if you planted a Magic Bean outside of Dodongo's Cavern as a child, you can ride the Magic Bean platform to reach it.
9. (Adult or Child/Day or Night) Kakariko Village - As a child, go up to the top of Death Mountain Trail after you get the Bomb Bag. The owl will be there. Talk to it to get a ride back to Kakariko Village. When the owl deposits you on the roof of a house in the village, turn right. The roof of the Cucco pen is below. Land on it and go into the crack in the wall to find a caged cow next to a piece of heart. As an adult, you can use the Hookshot to reach the roof of this house (the house that Anju the cucco girl stands next to during the day).
10. (Adult or Child/Day or Night) Zora's River - There is a Cucco near the entrance to the river. Carry it with you until you reach the area just before the blue Tektites. Go up the angled ramp, then jump toward the ledge that points toward the pillar with the piece of heart on it. You will have to throw the cucco when you get close to the ledge so that you can grab hold of the ledge with your hands. Climb up, then get the piece of heart from the pillar.
11. (Adult or Child/Day or Night) Zora's River - There is a piece of heart on a platform near the waterfall entrance to Zora's Domain, reachable either with a Cucco or the Hover Boots.
12. (Child/Day or Night) Zora's Domain - Light a deku stick in King Zora's room, head down the stairs and light the torch, head down and left and light the torch in front of the shop, go into the shallow water and light the torch here, then hug the far wall and walk behind the waterfall to light these two torches. A chest appears containing a piece of heart.
13. (Child/Day or Night) Lake Hylia - Go to the fishing pond, pay to fish, and look for the big fish hanging out by the log in the middle of the pond. That is the biggest fish; catch it and have it weighed to get a piece of heart.
14. (Child/Day or Night) Hyrule Castle Town Market - One of the Bombchu Bowling prizes is a piece of heart. Just keep playing until you get it.
15. (Adult or Child/Day or Night) Hyrule Field - In center of the fenced in area at the Lake Hylia entrance, a hole will open if you place a bomb. The Business Scrub inside will sell you a piece of heart for 10 rupees.
16. (Adult or Child/Day or Night) Gerudo Valley - Use a Cucco to fly toward the waterfall, or fall down to the ledge next to the river, and jump behind the waterfall and climb the ladder there. There is a niche behind the waterfall that has a piece of heart in it.
17. (Adult/Day or Night) Kakariko Graveyard - Ride the bean stalk to the ledge above, and roll attack the crate for a piece of heart.
18. (Adult/Day or Night) Kakariko Village - Go through Dampé's maze to reach the platform in the windmill that has a piece of heart on it.
19. (Adult/Day or Night) Zora's Fountain - On a block of ice floating in the fountain.
20. (Adult/Day or Night) Ice Cavern - Frozen in red ice in a room with falling icicles.
21. (Adult/Day or Night) Zora's Fountain - Equip the blue tunic and iron boots and sink to the very bottom of the fountain, where a piece of heart awaits.
22. (Adult/Day or Night) Lake Hylia - Ride the bean stalk or call Pierre the scarecrow and reach the roof of the lakeside laboratory. Climb the ladder for the piece of heart.
23. (Adult or Child/Day or Night) Kakariko Village - After collecting at least 50 gold skulltula tokens, visit the house of skulltula and talk to the fifth person there for a piece of heart.
24. (Adult/Day or Night) Death Mountain Crater - Enter the crater from the top of Death Mountain Trail. Go straight and climb down the wall straight ahead to find a piece of heart in an alcove.
25. (Adult/Day) Gerudo Fortress - Win at least 1000 points in the archery game behind the Gerudo Fortress.
26. (Adult/Day or Night) Gerudo Fortress - There is a chest on the roof of the Gerudo Fortress that contains a Piece of Heart. Use the Longshot or play Scarecrow's Song to reach it.
27. (Child/Night) Hyrule Castle Town Market - Use the Lens of Truth to win the treasure chest game (or just try your luck without it).
28. (Adult or Child/Day or Night) West of Hyrule Castle Town Market - Go to an area west of Hyrule Castle Town Market where there is a creek. Bomb one of the trees south of the creek to open a hole. If you have the Shard/Stone of Agony, it will react near that tree. Go down the hole, then use the Golden Scale or Iron Boots to reach the piece of heart at the bottom of the water.
29. (Child/Day or Night) Zora's River - Play the Song of Storms for the music-loving frogs to get a piece of heart.
30. (Child/Day or Night) Zora's River - After you have played all of your ocarina songs (not the warp songs) for the frogs, you can play their bug catching game. Win it to get another piece of heart.
31. (Adult or Child/Day or Night) Lake Hylia - Go into the Lakeside Laboratory. Using the Golden Scale you got at the fishing pond, dive down to the very bottom of the water in the lab. When you reach the bottom, you'll hear the Zelda "discovery" sound. After surfacing, talk to the Lake Scientist in the lab to get a piece of heart.
32. (Adult or Child/Day or Night) Gerudo Valley - As a child, you can pick up the Cucco in the area and jump off the left edge of the cliff to reach a crate on the far cliff that contains a Piece of Heart. As an adult, you can fall to the ledge across from that crate and use the Longshot on it to reach it.
33. (Adult/Day or Night) Desert Colossus - Plant a Magic Bean in front of the Desert Colossus as a child, then return to the Desert Colossus as an adult and ride the Magic Bean. The Piece of Heart is on top of the rock arch in front of the temple.
34. (Adult/Day or Night) Graveyard - Go back to Dampé's grave and race him. Use the Longshot on a torch in the second to last room to catch him in under a minute.
35. (Adult/Day) Kakariko Village - Use the Longshot on the roof of the building near the windmill and talk to the man there to get a piece of heart.
36. (Adult/Day or Night) Death Mountain Crater - Ride the bean sprout to the top of the first smoking pillar in the crater to get the Piece of Heart at the top.