Heart Pieces

Past E3 - This one can be found in the cave leading to the Maka Tree at the beginning of the game.  Just move the blocks to reach the Piece of Heart.

Past D5 - Once you have the shovel, use it to dig up the piles of dirt blocking the Piece of Heart shown here.

Present F5 - After taking the Power Bracelet from the Spirit's Grave, you can lift the rock blocking the path to this Piece of Heart in the cemetary.

Past A5 - Use an Ember Seed to burn the sapling here.  It will reveal a staircase leading to a Piece of Heart.

Past B3 - Look for a cave to the East of Restoration Wall.  If you have Roc's Feather, you can enter the cave.  Once inside, use Roc's Feather again to jump in a counterclockwise direction across the pits and to the Piece of Heart.

Present A1 - When you're standing at the location shown in the screenshot to the left, Play the tune of Currents or Tune of Ages to change to present time.  Once there, you will be able to find another Piece of Heart nearby.

Present E4 - Start out in the past, and make your way to the location shown in the screenshot on the far left.  Once you're there, play the Tune of Ages or the Tune of Currents to warp to the fenced off section of the store in the present.  Inside, you can buy a Piece of Heart for 500 rupees.

Present E1 - When you reach this room in the Goron Cave, bomb the crack in the wall to the right to reach another Piece of Heart.

Present G1 - When you reach this location in the past, play the Tune of Ages or the Tune of Currents to warp to the present.

Present F6 - Use the Mermaid Suit to swim below Crescent Island.  You will find an underwater maze with a lot of sunken treasure.  Eventually, you will find a Piece of Heart.

Maple-  Keep running into Maple whenever she appears.  Eventually, she will drop a Piece of Heart for you to pick up.

Gasha Nuts-  Eventually when you open a Gasha Nut, a Piece of Heart will be inside.