Stoic is a good overdrive for fighting stronger enemies as your overdrive guage charges as you take damage.
You get this Overdrive Mode as default.
Your overdrive guage charges when you attack an enemy when using this mode, you recieve this mode from taking damge from enemies.
Your overdrive guage charges as your allies take damage, this overdrive mode is gained when your party takes damage.
Your overdrive guage charges when you defeat an enemy, however this is usuless when fighting against one enemy. To get this Overdrive Mode you must defeat as many fiends as possible with one character.
Using this overdrive you overdrive guage charcges from defeating strong enemies, to get this mode you should defeat strong enemies in places like Omega Ruins.
Overdrive guage charges overtime, to get this you should use more turns than usual with a character by casting magic such as Haste.
Overdrive guage charges when a character is on critical HP, to get this fight often on low HP.
Your overdrive guage charges when you inflict a status disalignment on a fiend, to get this use Status inflicting attacks more often.
Overdrive guage charges when a character dies, to get this you must let your characters get KO'd often.
Overdrive guage increases when you have you status changed.
Allow a character to take as many status changing attack as possible. A good way to get this would be to fight a fiend that inflicts Stone or Poison.
Gained from fighting lots of battles, your overdrive guage goes up as you win battles.
Overdrive guage charges as you get hit with Status attacks, this is learnt automatically as you progress through the game.
Overdrive guage charges when you use Flee to escape a battle.
Your overdrive guage raises when you defeat a battle with one character, the best way to do this is have the other characters retreat.
Overdrive guage increases when you dodge an attack, the best way to get this is to have the Weapon Ability 'Evade & Counter' and get as far around the Sphere Grid activating as many Evasion nodes as possible.
Your overdrive guage rises as you heal more people in your party, to get this use healing magic or items often in battle.
Obtained by using spells such as 'Protect' on characters, your overdrive meter raises as you use defensive magic.