Duplicate Items and Units
To do this trick, you must have two final fantasy tactics advance cartridges and two game boy advances (or gba sp).

Link the two gba's and have one person (you) go into any kind of battle. When it's your turn to move, hit B to cancel the menu and press start to open up the sub menu. Now put Save Quit and it'll bring you back to the title. Now load your original data and NOT your battle save. After loading it, now both you and your friends, press start to go into the menu and select the ''Link'' option. Trade any items or units with your friends and after doing so, reset your game but don't save before doing it otherwise it'll erase your battle save. Now after resetting, load your battle save and you should still be during the battle. Either flee or defeat your foes and check your stuff. If done correctly, you should still have the same item or unit and your friend should have a copy of that item or unit. This will come in handy when trading secret characters or rare items.

Secret Characters
With the exception of Ezel, you must complete the game once in order to unlock the hidden missions.

Babus
Clear the Left Behind mission, then enter a town and clear the With Babus mission.

Cid
Clear all 300 numbered missions.

Ezel
Choose Gossip in the Card Shop, then clear the Reconciliation mission.

Ritz
Clear the Mortal Snow mission.
Shara Clear the A Maiden's Cry mission, then enter a town.

Credits
Beat the 300 standard missions and the extra Judge Missions