Explain the game, with a few examples of answers in search of questions. Ask, 'What's the question?', and get students to correctly say the corresponding questions for your answer.
Have two players--one from each team--come to the front. Style it like a game show if you like, with the students standing side-by-side. If you have access to bells or buzzers, it's even more fun.
Next, read an answer to a question and say, 'What's the question?' The fastest player to respond wins a point for her/his team. New contestants come to the front for a new round.
Rationale: This game forces the students to think backwards a little, so they must provide a grammatically perfect question. All too often, they are used to answering rather than asking questions, so this is challenging and useful as review.