Sentence mining from as wide a range of sources as possible. For example, computer error messages. You learn the subtle but important differences between the way technical matters are phrased in English, and the way they are phrased in another language. For example, "Este site pode estar temporariamente fora do ar ou sobrecarregado. Tente de novo em alguns instantes." "Instantes" instead of "momentos;" literally: "try again in some instants." It sounds weird to my English brain, but this is the same thing as "all your base are belong to us." Each language has its own logic, and its own arbitrariness.