When doing any exercise that involves a pressing motion before you even start the lift you must set up properly, the most crucial part to your setup is scapula retraction. Scapula retraction, as demonstrated in the picture below, is when you shrug your shoulder up then retract the scapula then shrug back done while keeping your scapula retracted. If you don't retract your scapula you will severely damage your shoulders in the long run.
