Body Sway

[Greengo]

I was an Army cadet 1977-1982 and attained marksman. To do this you slowed your breathing for minimal movement to aim, and held breath on moment of fire. I used this technique playing league snooker, and although I was never a great player, I won more than I lost. If you sway on a shot then your triangle (hand and feet) is too narrow. If your head sways then you can use your bicep/jaw - cue/chin contact to correct this.
Cue Crafty is spot on re boxer's stance.