Modifiers are words or phrases that modify or qualify another word or phrase.
Place a modifier as close as possible to the word or clause it modifies.
“Only” is a frequently misplaced word. The following sentence is ambiguous because it could imply either that Shakespeare wrote poems, or that he acted in plays. It is not clear whether “only” modifies “write” or “plays.” (Note that one can resolve the ambiguity when speaking aloud by stressing either “write” or “plays.”) The second sentence is unambiguous; “only” must modify “plays” and the sentence therefore implies that Shakespeare also wrote other kinds of texts.
Weak: Shakespeare did not only write plays.
Better: Shakespeare did not write only plays.
Other frequently misplaced words: “either . . . or”; “neither . . . nor”; “both”; and “each.” Make sure that both clauses modified by “either,” “neither,” “both,” or “each” are grammatically equivalent.