Very minor spoilers.
1. Beat game on normal, then play Hero Mode.
2. Buy lots of bait and give it to the fish on every island.
3. Get the Swift Sail at the Auction House after Dragon Roost Cavern.
4. Get lots of Rupees.
4.1. After getting the Wind Waker and beating the first dungeon, go to the guy dancing by the gravestone, and talk to him. He'll say something, then pull out the Wind Waker and learn the song. Go to the back of the bomb shop and cut the grass and break the pots for Rupees. Then play the Song of Passing and keep doing it until you get to 500 Rupees.
4.2. After getting back to Outset to get to Jabun, go to the area with the bridge and make the wind's direction go west. Then fly over to the forest and use the bombs to break the big rock and go in. You'll get to carry up to 1,000 rupees.
5. After finishing the Forest Haven, go 2 sqaures east from Outset Island and go to the area with the Seagulls. Fight the Big Octo, and you'll get double magic. Fight it with the Boomerang.
6. Look up a guide for Pieces of Hearts and Treasure Charts.
6.1. When you get some Treasure Charts, go to the places with the treasure when you can.
7. Check your mail whenever there is mail.
8. When you need to get to the Private Oasis, get 20 or 21 Joy Pendants (Use the Grappling Hook on Moblins) and give it to the Teacher at Windfall Island.
9. When you need to get on the Ghost Ship, the Ghost Ship Chart is on Diamond Steppe Island