These targets are easy to make, accurately represent the average upper torso, hold up better than paper and are easier to put up and use outdoors in the wind.
Start keeping and collecting cardboard as close to or larger than 18″ x 30″ whenever you can. Take some time to mark out and cut the first one. Keep it for a pattern and from then on you are just tracing and cutting.
Use this target by itself, it will help you learn to focus and pick a spot in the center of mass. you can also staple your own targets to it or to really mix it up, hang an old t-shirt over it and see how well you pick a spot center of mass.