Heroic abilities will trigger only once per spell, even if that spell targets the creature with the heroic ability multiple times.

Heroic abilities will resolve before the spell that caused them to trigger.

Heroic abilities won't trigger when a copy of a spell is created on the stack or when a spell's targets are changed to include a creature with a heroic ability.

If a card in a player's graveyard has in its mana cost, X is considered to be 0.