First of all for this cheat you need to have the W-item materia found in Bone Village which is ner the "north pole" of the map(looks like a cow's skull laying on the ground. tell the worker that you want to find "normal treasure". send the diggers to the top half of the village, at the lower left hand corner of the little tent. (this may take a while) inside of any battle, go to the W-Item command and select the item you want to duplicate (you must have at least two). then select the character. then choose the same item again, but instaed of pressing the circle button to select the character, press the X button. The item should have increased by one. repeat as necessary!