First, you do not encroach on personal space, nor do you present a confrontational position. Second, you offer the person a perceived “escape route,” so he doesn’t feel trapped. Finally, you allow at least one leg-length (about three feet) as a personal safety margin.
Another element of body posture is the positioning of your hands. Many times the individual will be focusing much of his attention on your hand placement. Avoid concealing your hands behind your back. This can be perceived as a threatening pose, but more importantly, the irrational person can imagine you have something dangerous behind your back. It is not unlike the irrational thought process to imagine that you’re holding a gun or knife. Also, keep your hands out of your pockets. They will not do anyone any good resting inside your pockets if the individual escalates and becomes physically aggressive. Keep your hands out in plain view, at your sides if possible.