Hyphens, En Dashes, Em Dashes

Q. I realize that the rules regarding hyphenation are fluid, but I was wondering if you could clarify an issue that has been bothering me. Is there a good way to know when to hyphenate two words serving as an adjective, especially when ambiguity could be an issue? For example, would the phrase “foreign language skills” be hyphenated? What about “large book sale”? Could this second phrase be interpreted as “a sale of large books” instead of “a large sale of books”?

A. If a hyphen can save you from ambiguity, then go for it. That’s what hyphens are for. If a hyphen wouldn’t help (as in “large book sale”), then rephrasing as you have done will fix the problem.