If you want an easy way to revive fallen characters, try the following. Head to Balfonheim Port later in the game, when a gambit called Ally: Status=KO can be purchased. This can be used in conjunction with Phoenix Downs or the Raise spells to raise dead characters automatically. However, if you use the gambit called Ally: HP < 10%, and combine that with a Phoenix Down or the Raise spell, your allies will revive one another before they even disappear after being KOed.