Instructions
High/Low Leveling
Enter an easy battle with a mix of high-level and low-level characters. Make sure you have at least one character capable of healing. Additionally, remove all of your characters' weapons before the battle.
Destroy all of the enemies except for one, preferably an enemy unit who will do very little or no damage. If you cannot defeat these enemies without weapons, try using magic or weak weapons instead.
Order your low-level characters to attack your high-level characters. Because of the level difference, your low-level characters will gain an accelerated experience boost.
Heal your damaged characters. The healer will also gain experience. Because the attacking characters have no weapons and deal little damage, you will not have any trouble keeping everyone safe.
Automated Leveling
Turn off all battle messages in the "Options" menu. These options are the sixth through ninth options in the list.
Enter a battle in a flat, open map such as Zeklaus Desert or Mandala plains.
Set up your team with the black mage ability "Toad" and the knight abilities "Rend Power" and "Rend Speed." Additionally, make sure every character on the team is equipped with the squire ability "Focus." Some story characters cannot learn "Focus" and will not be suitable for this trick. Do not bring any characters with the "Throw" ability.
Kill all but one of the enemies on the map.
Cast "Rend Power" and "Rend Speed" on the remaining enemy repeatedly until it has only 1 point in both stats. After that, cast "Toad" to fully disable the enemy.
Repeat the "Rend Power," "Rend Speed" and "Toad" rotation on all of your own characters.
Send your characters as far away from the enemy unit as possible.
Open the "Options" menu in the middle of the battle and turn on AI control. Set your characters to the "Coward" setting. For any black mages on your team, set them to "Defender."
Watch your AI-controlled characters sit in place and cast "Focus" forever. Each time the ability is used, the character gains a small amount of experience. You can plug in your PSP's charger and leave it running overnight.