I like what Sammy Franco writes
Before launching your first strike, you must assess the source of danger. Who is posing the reasonable threat? Is it someone you know, or is he a complete stranger? Is it one person or two or more? What are his intentions in confronting you?
Pay very close attention to all available clues, especially nonverbal indicators. Your answers to these important questions will shape your overall tactical response.
There are five essential factors to consider when assessing a threatening adversary: demeanor, intent, range, positioning, and weapon capability.
1. Demeanor. What is the adversary's outward behavior? Watch for both verbal and nonverbal clues. For example, is he shaking, or is he calm and collected? Are his shoulders hunched or relaxed? Are his hands clenched? Is his neck taut? Is he clenching his teeth? Is he breathing hard? Does he seem angry, frustrated, or confused? Does he seem high on drugs? Is he mentally ill or simply intoxicated?
What is he saying? How is he saying it? Is he making sense? Is his speech slurred? What is his tone of voice? Is he talking rapidly or methodically? Is he cursing and angry? Remember that all of these verbal and nonverbal cues are essential in accurately assessing the assailant's overall demeanor and adjusting your tactical response accordingly.
2. Intent. Once you have assessed the adversary's demeanor, you're in a much better position to assess his intent. In other words, why is this person confronting you? Does he intend to rob or kill you? Is he trying to harass you?
Is he seeking vengeance for something you have done? Or is he a troublemaker looking to pick a fight with you? Determining the assailant's intent is perhaps the most important assessment factors, but it also can be the most difficult.