There is a difference between doing an exercise with proper form and technique than just mindlessly aiming to complete a certain number of reps.
One exercise so many people butcher is the bicep curl. You will often see someone using excessive momentum to lift the resistance.
Here is a few of the coaching cues and the video below.
1. Focus on the muscle and contract and squeeze at the top of the movement.
2. Eliminate momentum. Don’t use your hips or back to lift the weight (that only works your ego 
????)
3. Breathe! Don’t hold your breath. Breathe faster towards the end when it starts to get harder.
4. Keep the head and neck in neutral. (I actually lean forward a little here which I should’t do!)
So many people butcher this exercise by using momentum and hip movement.
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