Instructions
Put distance between yourself and King Boo. King Boo often stands in place before he begins his attacks, so use that time to run away from him.
Run behind pillars. King Boo's blow attack will not hurt you if you are behind a pillar.
Get behind King Boo. King Boo can only blow in one direction, so go behind him to avoid his attack. This strategy is most effective if you are too close to King Boo to run away from him and there are no pillars nearby.