Utilizing some form of cover screens part of the body. Most people would instinctively shoot for the centre of the visible mass, making for a smaller target.
I learned this in IPSC with partial targets when we actually engaged targets as far as 50m in 'draw & fire' exercises. On closer targets, people would forget that all they had to do was hold lower, even if that portion of the target was missing.
The other prop frequently used in westerns are the ever handy wooden barrels, boxes, paper thin walls, water troughs, etc. At least the water in the trough would have the effect of slowing bullets.
Our club put on a couple of "corporate day at the range" events that included demos of CAS and IDPA. People commented that now they knew just how much BS Hollywood feeds the public.