Imagine there is a line drawn from each face to the next. Try and position them so that no head is directly on top of, or beside (same level) another. Make diagonal lines not totem poles. Use props to seat some people or bring some small folding stools. Have some people sit down, or stand up on something. Use what is naturally in the environment to pose them, or if you have nothing available just arrange them so the heights are staggered.