Cast this spell only before blockers are declared.
Target creature gains first strike until end of turn. If it doesn't have rampage, that creature gains rampage 2 until end of turn. (Whenever the creature becomes blocked, it gets +2/+2 until end of turn for each creature blocking it beyond the first.)
If a turn has multiple combat phases, Rapid Fire can only be cast before the beginning of the Declare Blockers Step of the first combat phase in that turn.