Most efficient Chapter One JP farming?

To summarize and add to what Krazer has stated:

General Farming in FFT:

It's pretty much always the same no matter how you do it. Use reduced damage attacks and heal. Rinse and Repeat.

Skills: (that are beneficial to farming)

• Frog. Reduces units attack to 1 (usually if they have a high enough Physical attack is my be a bit more).
• Potions. If cash isn't an issue then swing-away. Just get a chemist and throw them potions.
• Breaks/Ruins. Speed Break will reduce the number of turns the enemy gets so they can't attack you as often. Power & Mind Break will reduce the units Physical and Magic damage to a really low amount allowing for simplistic farming.
• Steal Experience. This along with any Steal skill is a no brainer. A word of caution with Steal Experience though. Don't use it too much or you'll find yourself vsing lv 20s when most of your party is lv5. I made this mistake once. It resulted in 5+ hours wasted haha.
• Gained JP Up. I'm not even going to bother explaining this one, it should be obvious.
• Auto-Potion. For those of us who can't resist the JP-Glitch you probably have this from the start. Disable it. It's a potion that is used but doesn't yield experience. If farming is your goal, disable it and heal as an action.
• Steroids. All skills that buff you permanently. i.e. Accumulate, Yell, Scream. Sadly the Squire ones are the only ones I can think of, but I don't seem to recall any non-squire ones so this might be it.
• Calculators. (I know they're not really Chapter 1 available but I figured it would be worth mentioning) Their spells cost no MP. Spam them everywhere.
• Chakra. The monk skill chakra heals HP & MP. This is a great way to avoid the cost of potions if you put them in combination with a priest or just use Chakra only to heal.
• Equip Change. Free skill, trap an enemy, and unequip your weapon for low damage and the same amount of Exp/JP. Finally a use for this :P

As you can see nearly any skill can be used as a farm-tool, you just have to know what is available and accommodate.