I look for the kind of text that doesn't look like the writer I'm considering. Plutarch is a great example.
John D'AgataPlutarch's peers were writing "rhetorics," which were these dry philosophical treatises that made really broad gestures about life and death and fate. Plutarch stepped out of the stream to create an essayistic form that relied on a digressive structure and down to earth anecdotes.
John D'Agata