Silver Apples and Soma Drops carry over between playthroughs, so don't use them on the first playthrough if you're planning to max stats on NG+.

Bardsongs that buff the party prevent the bard from taking any other actions until the song wears off or the bard is physically attacked.

Counter augment ability counters physical attacks with whatever ability is equipped in the first (non-auto) ability slot.

Talking to a yellow chocobo lets you ride it on the world map, avoiding random encounters. It will leave when you get off.

Talking to a black chocobo (not present in all forests) lets you fly on it around the world map. You can only land in forests and the chocobo will wait for you to return, but as soon as you do, it will fly directly back to the forest.

Talking to a white chocobo recovers MP for the whole party.