im a draganov sniper (Dont know if its the same with all)
if there standing i shoot where there chest would be if they wernt on lean . or even the legs
if they are crouching. i shoot where the balls would be
and if they are prone shoot a little opposite to the way they lean
(this helps on places like crossfire .. maps where you are shooting through walls ... but metal shipping containers you cant do much about... what i sugest is KNIFE THE BASTURD)