Cut the cardboard square down to a size that serves as the wheel's base, and can either be pinned to a wall or laid flat on a table. The size of the base should be slightly larger than that of the spinning wheel.
Using a protractor or large circular object, trace a circle on poster board. Cut the circle out of the poster board. The size can be any desired, but should be large enough to legibly write the prize possibilities around it.
Use a ruler and pencil to draw lines across the circle that all intersect in the middle, as though drawing pie slices.
Use markers, paint, or any desired medium to label and decorate the sections drawn on the circle. Each section should have a specific prize, instruction, or label. Examples of possible labels could be "pick three pencils from the prize table," or "spin again."
Use the pencil again to poke a hole in the center of the poster board, and the center of the cardboard base. Spin the pencil point around to make the hole wide enough to allow the wheel to spin on its axis.
Insert a brad into the two holes, layering the poster board on top of the cardboard. The hole should be lose enough that the brad can turn freely when the wheel is spun with enough force, but not so lose that the wheel will spin too long.
Mark a point on the base with a small arrow that indicates the designated "prize" when the wheel ceases to spin.