Both lifters try to pull too far and too high on vertical pulling motions such as pull-ups and lat pulldowns. Rather than trying to touch the bar to your chest or reaching your chin over the bar (both of which can produce dysfunctional mechanics), the goal should be to achieve proper upper back and lat activation.
Increase starting strength with this lift. Bring the bar down controlled and rest it for a half-second without letting the bar sink. Accelerate with as much force and speed as possible.