Print the attached template on card stock or stiff paper and cut out triangular fangs. You can make them as long as you like, but I think 10-12 cm (4-5 in) looks best. They all don't need to be the same size, either. If you don't have a printer, you can cut out paper fangs and then use a permanent marker to color it in.
Fold the fang along the black edge. This is to help camouflage where you attach the fangs to your face.