Start with a rectangular sheet of newspaper, and fold the top of the paper towards the bottom.
Fold one of the top corners towards the center of the paper, and crease the fold. This fold creates a triangle at the top and leaves a few inches of paper unfolded at the bottom. Fold the other corner at the top towards the center, and crease the fold. The two triangles can overlap. If needed, use a piece of tape to hold triangles together.
Using the top layer of the paper, fold the extra margin at the bottom towards the top, and crease the paper along the base of the triangle. If the bottom margin of paper is extra long, fold it down to create a reasonable sized brim. Flip the hat over, and repeat the folds for the brim on the other side.
Pull the hat open, and try it on. If needed, add tape to hold any of the folds in place.