The art of Spanking.
Spanking is not JUST smacking someone anywhere. Knowledge of anatomy, intuition and empathy, as well as trust and an internal ‘goal’ should be things in your toolbox that are always utilized. * I, myself, have enough background and experience to understand and confidently practice “Kink Therapy”, which involves therapeutic spanking as part of a healing session.
The others, I feel are more easily learned and much more common in scenes between couples (beside the critical precision of hardcore flogging/spanking/whipping), and not nearly as important to ‘get right’ for the health of the spankee on a psychological basis.