Great way to level up
Using this technique, I got all four of my characters to level 99. You have to have access to the Crystal tower to do this. I also recommend doing this with a single character. OK, here it goes...
Get your character to walk around until he/she enters a battle. Do this until you get into a battle with monsters called Bluck (they're purple and have weird whisker like things). Kill all of them EXCEPt for one. Now, just guard until it summons a Kum Kum (light purple hooded thing), kill the Kum Kum, and guard until the Bluck summons another Kum Kum. A lot of the time, you won't need to guard because the Bluck will summon Kum Kum's several times in a row. Just do this until you feel like you gained enough experience (I gained 1.5 million with one character in 20 - 30 min). You might also want to switch your character to a Black Belt so you can get to 9999 hp.
More tricks, tips and cheats for this game are right here - Final Fantasy III cheats
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