Position your feet evenly on the platforms and position yourself against the padding.
Drive one leg straight back, then bring it forward.
Drive the opposite leg back as the other leg is coming forward and repeat.
Rushing repetitions.
Lacking control.
Moving the upper body too much.
Have the balls of your feet placed on the platform and heels hanging off it.
Drive your heels upward to lift the weight.
Steadily lower the heels down until your calves are fully stretched and repeat.
Using momentum to drive the weight up and down.
Feet being too wide or narrow, keep it should width.
Upper body swaying with the movement, keep it still.