There isn’t necessarily a right or wrong way to perform an exercise however, there are safe and unsafe versions, which are either effective or not effective at helping you, reach your goals. Far too many trainees are using sloppy form and only performing partial reps. Dean Somerset, author of Post-Rehab Essentials says, "seeing bent over rows with spines that resemble a question mark, pull downs with a chin poking forward over the bar, and squats that look more like a hockey goalie in the butterfly stance is unfortunately too common." Somerset explains that there is a science to exercise and lifting biomechanics upon which the body will function optimally while minimizing injury risk to its joints and soft tissues.
If you’re willing to spend hours in the gym and all your hard earned money on gym passes and supplements, invest in a personal trainer or strength coach to teach you how to exercise correctly and safely. Remember, partial reps are only going to give you partial results.