Also, using the up/down buttons on the D-pad cycles between your party members in the order they appear in the party list (so is usually the best way for healers to target healing, though the "Friends" filter for left/right button cycling can be useful places like big fates where you might want to heal or raise someone not in your party).

And L1 + up/down cycles through the enemy list, which can be useful for tanks if they need to grab back enmity from one of them.