Flash cards.
Take one set, and draw up and airplane flying over the four squares at headings of 0, 45, 90, 135, 180, 225, 270, and 315.
Take another sheet, draw about 12 sets of four squares with a N, S, E or W next to them. This is your answer sheet. Mix up the first set of cards and flip through them, marking the North, East, South or West squares as indicated by the N/S/E/W on your answer sheet. Repeat. You'll notice a pattern.