The SM-Leather-Fetish communities recognize the phrase "Safe, Sane, Consensual" as the best brief summary of principles guiding SM practices:

Safe is being knowledgeable about the techniques and safety concerns involved in what you are doing, and acting in accordance with that knowledge.

Sane is knowing the difference between fantasy and reality, and acting in accordance with that knowledge.

Consensual is respecting the limits imposed by each participant at all times. One of the recognized ways to maintain limits is through a "safeword" which ensures that each participant can end his/her participation with a word or gesture.