3.d4 and 3.Bc4
Black's 2...f6? is a weak move that exposes Black's king, weakens Black's kingside and takes away his knight's best square. The moves 3.d4 and 3.Bc4 are strong replies; I.A. Horowitz wrote (substituting algebraic notation for his descriptive notation), "Simple and potent is 3.Bc4 d6 4.d4 Nc6 5.c3, after which Black chokes to death."
Read more about this topic: Damiano Defence