Poke a pin hole in one piece of cardboard, and get a second piece of cardboard/white paper/etc. Hold the two pieces a couple of feet apart and play with them a bit to get them parallel to each other and aligned with the sun. The light that comes through the pinhole and shows up on the second piece will show the sun, which will be crescent shaped as the moon covers it. It doesn't need to be big and the hole doesn't need to be perfect. My pieces were about the size of playing cards, and I poked the hole with a small Phillips screwdriver like you'd use on eyeglasses or electronics.