Another trick you can use is find a random battle and kill all enemies on the battlefield except one. Beat it up but don’t kill it – let it attack your party and just have them use potions on themselves. This allows you to milk a little more exp and JP out of a battle than you would otherwise get (a good battle for this is against Yellow Chocobos on Mandalia Plains – when they’re weak they use Choco Cure on themselves, thus if you weaken them they’ll keep curing themselves, allowing you to drag the battle out and get more exp and JP as well. 🙂
Soldiers – Gained JP UP + Accumulate
Ramza – Gained JP UP + Yell
Don’t kill the last enemy of a normal battle and then move your party away from the enemy and have them to cast these skills, and you’ll be farming JP like a boss.
Don’t forget to set Basic Skill as a secondary action command while changing jobs.
That’s it.