There isn't a trick. You just keep playing until you learn the game. The computer (playing for the old man) will eventually let you win when you play fairly well.
(Some hints at the related question below)
go to blue moon mountains and beat the man at mancala the fall to the bottom of the cave and its at the right bottom corner.
At the Mountains of the Moon, you have to climb the mountain to the ice cave. Beat the old man at "mancala" and you can enter the cave. You will find the cellphone and the Red Jewel.
The red jewel is in a cave at the Mountains of the Moon, and you must beat an old man at mancala to enter the cave. (see related questions)
Not a hag, just an old wizened hermit. He's atop the Mountains of the Moon. His cave has the cell phone and the red jewel. But you have to beat him at the game of mancala.
There is no known security code on Nabooti Island.
You don't trade anything. You find the cell phone in the ice cave at the Mountains of the Moon. You have to beat the old man at mancala. (see related question)
play a different island
The old man is in front of the ice cave at the top of the Mountains of the Moon. Beat him at mancala to enter the cave, where you find the Red Jewel and a cell phone. (see related question)
When you go to the Mountains of the Moon, you play mancala against the old man at the cave. Beat him to enter the cave. The red jewel is at the far right and the cell phone is at the bottom left of the cave.
type in nabooti
You have to go to mountain of the moon, beat the man at mancala, and at the bottom left of the cave is the cell phone. Hope this helped!
The Nabooti totem, in the museum on Nabooti Island. Five of the seven jewels were removed and are hidden in areas of the island. You have to recover the jewels and put them back on the totem to beat the island.