Any time after you've got your sword, slash the bushes and fall down the Mabe Village well for a Piece of Heart.
Sword
Head into the first Mysterious Forest cave, the one on the way to the toadstool, to find this piece.
L-1 Bracelet
After getting the Roc's Feather, jump onto this platform to claim your third Piece of Heart.
Roc's Feather
North from Bow Wow's house you can talk to a man and play the fishing minigame. Catch the large fish closest to you for a heart piece. You may have to clear out the other fish first by catching them too, so bring plenty of Rupees.