On many 3x5 cards I put a problem and an answer, but they do not match. I start the students out by putting a question on the board. Someone has the answer on his/her 3x5 card. They walk up and put the answer on the board and also put up the next question (the question on their card). I give them a new card and they sit down. The process continues and everyone eventually gets up to the board. You could also do this in reverse order for another lesson.