Golden Sun - Side Quests

Before Entering Lamakan Desert - Alpine Crossing - Saving Hsu
Use Reveal to uncover a hidden door that will allow you to reach Hsu. Use Lift on the boulder that is crushing Hsu to save him. The rocks at Alpine Crossing will be cleared making a shortcut to Altin and Xian.

After Reaching Venus Lighthouse from Tunnel Ruins - Further Exploration
There are more items inside of Tunnel Ruins that you cannot reach in just one trip. When you first reach Venus Lighthouse after going through Tunnel Ruins, go up the far left staircase. Use Move to put the statue on the circle to its right. Go down, use Reveal near the staircase, and go up the hidden staircase. Press "A" on the statue at the back of the room. Go back to the Road to Babi's Lighthouse and enter Tunnel Ruins. You will be able to find Asura's Armor by using Reveal near a statue. You will need Move, Douse, Frost, and Reveal in this part of Tunnel Ruins.

Tolbi - Tolbi Slot Machine
While you are in Tolbi, you can win special items from the slot machine above the inn. All you have to do is line up the icons. Moons are wild, shirts win undershirts, rings win rings, boots win boots, stars win items, and hearts win items. The following are the Tolbi Slot Machine prizes. Shirts: Silk Shirt, Mythril Shirt, Running Shirt. Rings: War Ring, Adept Ring, Sleep Ring. Boots: Fur Boots, Hyper Boots, Quick Boots. Stars: Elixir, Water of Life, Psy Crystal. Hearts: Nut, Potion, Vial.