Holding dumbbells in each hand, hinge forward so your back is almost parallel to the ground.
In an arc motion spread your arms out from each other until they're aligned with the shoulders.
Slowly retreat back the same path back to the start position and repeat.
Extending too far past the shoulders.
Not maintaining a consistent arm bend.
Rushing repetitions.
Hang from the bar with an underhand grip, spaced just wider than shoulder width.
Pull up by brining your elbows to the back of the hips until chin is level with bar.
Slowly lower back to start position and repeat.
Swinging to get up.
Dropping on the way down.
Uneven grip.