If you’re not sure how to perform an exercise correctly go to any large gym during peak hours and watch how most people do it. Pay close attention to how they are positioned and how they move. Pay attention to things like their speed and timing, where and how long they stop to hold or pause, etc. Ask some of the people working out and the personal trainers for tips on doing the exercise and take detailed notes.
Then convert your notes into a list of bullet points on how to perform the exercise. Next to this list write the exact opposite of each of those bullet points. If you use these opposite bullet points as a guideline for performing the exercise you’ll end up with something much closer to the correct method.