Lay the paper down vertically and fold it from left to right so that its corners meet up. You can use ordinary white printer paper, construction paper, or origami paper. This is called folding the paper "hot dog style." Make a neat crease along the paper. To strengthen the crease, run your finger down the fold 3-4 more times.

Summary:
Fold an 8 ½ in x 11 in (21.5 cm x 28 cm) sheet of paper in half.