44. What you need: Zora Mask, Great Bay Title Deed
Right when you enter the area with the broken bridge and two octoroks, go right and find the Deku Scrub. Talk to him as Zora Link and give him the Great Bay Title Deed to get the heart piece on the opposite ledge.
45. What you need: 30 rupees
Go to the Spirit House behind the Music House and play the Poe Catchers game. Defeat all the Poes to get a piece of heart.
46. What you need: Deku Mask, Hero Bow
On the rooftop of Ikana Castle, find the ledge on the right with a switch. Shoot the switch with an arrow to stop the flames. Now use Deku Link to fly across to the piece of heart.
47. What you need: 16 heart containers
At the bridge with the two octoroks, take a left to get to a waterfall. Go behind it and fight the bosses in the four rooms. Defeat each to get 100 rupees, then go back out and the Poe Catcher will give you a piece of heart.
48. What you need: Captain's Mask
At the Ikana Graveyard, talk to the stalkids guarding the big grave on the night of the second day and ask them to break the grave. Jump in the hole and find your way to the piece of heart.
49-52. What you need: Every Mask in the game
To get the last four pieces, just play through each of the little kids dungeons inside the moon. Each one has a piece of heart.