Hint: Stay on the Island
On the deserted island after the ship is wrecked you can convince your party members to stay on the island and live there. Eventually they will agree and you will become stuck on the island. The character portraits will also be different. Note: This will end your game so have a saved game before deciding to stay.
Hint: Deserted Island
If you are trying to collect all 108 stars of destiny then you'd better listen to this. Finding the island would be a difficult task if you didn't know where it was. Just head west of Nay and always look to the ship's right. After you sail for awhile you will see land. Head towards it and you will be back at the island. Coming here will enable you to get two new characters. Good luck with the other 106.

Hint: Easy Money
Want to level up your characters' weapon or buy better armor? Instead of defeating a lot of enemies for a quick buck, stock up on crystals/pearls at the various trade stands on the different islands talk to the guy by the trading stand in Nal-nal Harbor. He will most likely tell you that one of the items is being sold for tons of money. After he does, sell which ever item is mentioned and you can make up to 340,000 potch at a time especially if it is pearls!

Hint: Steal the Kings Clothes
Some point in the game after you get your headquarters out to sea go to lin en kuedos room and search the closets in there you will find the fancy garbs. At the end of the game when the king is going back to Obel Flare he will look for his clothes and will not find them. So the king will wear his normal clothes instead of the fancy garbs because you stole them

Hint: Deserted Island part 2
Another way to find the deserted island is to look in the Suikoden 4 handbook that shows a map of all the islands. Just look for the Kingdom of Obel (it's the largest island in the picture), go northwest to find Mordo island, finally look at the map to see the island northwest of Mordo island and you'll see the deserted island.

Hint: Treasure Maps

Map 1 Doughnut isle:Talk to Rene
Map 2 Middleport underground path
Map 3 Iluya Kooluk army advanced base
Map 4 Hermitage island:The shed to the right of Elenor's house
Map 5 Mouse chase in Nay-Kobald, Average/shiny
Map 6 Nay island: cheif's house, the bookshelf
Map 7 treasure chest in stonecutter's field
Map 8 pirate's nest: treasure chest
Map 9 Lime Shelf island: treasure cheats
Map 10 Razril (back street):crate
Map 11 Na-Nal (harbor):Treasure chest
Map 12 Misty Merchant ship:cabin table
Map 13 Kingdom of obel:Barrel on the right side of the dock
Map 14 Game of tops with Basil (20 wins)
Map 15 Pirate's nest: small chest on the beach
Map 16 Iluya island: treasure chest
Map 17 Nay-Kobald: tree behind the hot spring
Map 18 Na-Nal(hillside town): next to armour shop
Map 19 Middlleport inn: near barstool in the corner
Map 20 Kooluk advaced base: stack of crates
Map 21 Nay island: treasure chest
Map 22 Hermitage island: in back of the cave
Map 23 obel patrol ship: behind Flare
Map 24 Na-Nal(harbor):basket on the wooden boat
Map 25 Razril inn: bookshelf
Map 26 Mordo island(seashore): Next to the hot spring
Map 27 Nay island inn: treasure chest
Map 28 Na-Nal rune shop
Map 29 Ruins of Obel, outside: tree
Map 30 Treasure chest, Razril hall of knights(rooftop) after city's liberation

Hint: Big Money With Ancient Crab
To get big money you must have two things. You need to have Noah your support character and one of your party members need to have the prosperity rune equiped. Go to the deserted island and battle the Ancient Crab. When you defeat it you'll 30% more potch because of Noah which will come up to 32,500 potch. But because you have the prosperity rune, it dubles the amount of potch you get to a whomping 65,000 potch. Now you can but armor, upgrade weopons, or just spend it how you like.