You can bypass a forced encounter if you enter the tile while it's being occupied by a random battle monster. Instead of fighting through the forced encounter you will fight a random battle. After the battle, you can simply step off the tile and continue.
Stay alive after a fatal hit
If you fall off the side of the screen when you get hit, you won't die, even if your HP is at 0. Stand very close to the edge of the screen, and attack from there. You can use this to level up without the risk of losing your EXP to a gameover. Especially at screens with jumping fish.
Unlock Fairy
Find the Water of Life behind a boulder in the swamp, take it to Mido.
Unlock Fire
Examine the fountain in Nabooru then talk to the thirsty woman.
Unlock Jump
Find the Trophy north of Zelda and take it to Ruto.
Unlock Life
Find a mirror in an empty house in Saria and take it next door.
Unlock Reflect
Find the child in the origin of the river in the maze and take him to Darunia.
Unlock Shield
Talk to the old man in Rauru.
Unlock Spell
Talk to the old man in Kasuto (you must hammer a tree in the woods farthest to the east).
Unlock Thunder
Once you have everything else, talk to the man in the old ghost town of Kasuto.
Bypass forced encounters...