Anchor yourself on the machine, adjusting the thigh pad.
Sit with the tip of the spine pressing against the back rest.
Lean forward and hold on to the machine handle.
Breath in on top and curl the weight through full range while keeping a neutral spine.
Slowly bring the weight back to the starting position and repeat the movement.
Don't allow momentum to dictate the tempo of the exercise.
Control the movement throughout the entire range of motion.