You never mean: Could care less
You always mean: Couldn't care less
Why: You want to say you care so little already that you couldn't possibly care any less. When the Boston Celtics' Ray Allen said, "God could care less whether I can shoot a jump shot," we know he meant exactly the opposite because 1) God has other things on his mind, and 2) God is a Knicks fan.
Read more (courtesy Shine)