In some books, I've seen the EM dash placed before an exclamation mark/question mark. In other books, I've seen it placed after it. Is there a correct way of doing this or is it a stylistic choice or are there different situations when one is used oppose to the other? Examples from Harry Potter the 7th book: "Don't you dare --!" squealed Aunt Petunia, but again, Vernon waved her down: slights on his personal appearance were, it seemed, as nothing to the danger he had spotted. Another one: "Know how to --? Of course I ruddy well know how to driver!" spluttered Uncle Vernon. Example from Harry Potter 5th Book 'I know, Williamson, I know, I saw him too!' gibbered Fudge, who was wearing pyjamas under his pinstriped cloak and was gasping as though he had just run miles. 'Merlin's beard -- here -- here! -- in the Ministry of Magic! -- great heavens above -- it doesn't seem possible -- my word -- how can this be --?'