The Flaw: Lowering the bar too far and rounding the lower back, a lumbar injury in the making.
The Fix: Don’t concern yourself with reaching a certain point on your shins. Instead, lower the bar as far as you can while keeping your back flat, whether that ends up being mid-shin or just below the knees. Greater flexibility will come with practice.
The Flaw: Locking out the knees.
The Fix: Your legs should stay straight, but not completely extended. Keep a slight bend in the knees to take some tension off the lower back and better engage the hamstrings.
The Flaw: Lowering the bar too far out in front of the legs.
The Fix: Slide the bar straight down your legs so it practically brushes against you. To make this happen, initiate the movement by pushing your hips back as you lower the bar.