Before I had covered how to survive a terrorist attack, that was after the Paris attack. That told you to react but not like a spaz. Hide or stay still as we predators are attracted by movement.
I also told you that the best defense is to avoid trouble in the first place and that by reading the situation you can see if there is something out of place and thus mentally prepare you to act rather than to freeze like a deer in the head lights.
During my time oppressing savages for crown and cuntry we'd have to do foot patrols. It was often dark or we'd approach the person from a distance not able to see their faces. Faces can lie if they are trying to look normal, sure you can't hide the wild eyes, shallow breathing and sweating but from a distance all you have to go on is below the neck.
There is no excuse for the pants though.
The way a person is dressed often gives away their intent. Why do you think those ghetto rats wear clothes two sizes too big? Aye sure they all have body issues and barf up their bucket of Popeye's chicken after they eat it.
You can hide things in baggy clothes. You can't hide yer love handles but you can hide yer 9 mil gat doon yer arse crack. Or yer bomb vest under yer puffer jacket.
Like all those poker films, even street hoods have tells. How often do you touch yer phone or yer wallet in yer pocket? Yer checking it's still there but that checking can become a reassurance thing if you are stressed. The bad guy will keep patting his hidden weapon which is why you always watch the hands.
Those cowboy movies have the gunslinger looking at the other guy's eyes to tell when he is going to draw ... that would be just a movie and used for dramatic effect. If the guy goes dead eyed he'd have drawn and shot by the time our hero registered it. Watch the hands, see if they are empty and you can tell so much from gestures as to whether or not this person is aggressive or submissive.
The reason we shake hands to to show there is no weapon in our sword hand (usually the right hand)
Unless you spend years immersed in another culture you won't fully understand it. Human nature is universal though so it doesn't matter if they have some strange ways.
People are driven by the same things, power, sex, money and sausage rolls. We all have that freeze, fight or flight instinct. The guy approached by the foot patrol does he freeze for a second before continuing? He's decided to fight, or bluff his way through.
When standing in Walmart and some mouth breather stands too close to you a lot of people will inch away, that is the civilized version of the flight response or you freeze and hold yer breath and hope they go.
People are naturally lazy, predictable creatures of habit. In survival situations you'd always take the path of least resistance as to not use up energy. People buy the same stuff, talk to the same people and go to the same places, even when they try to be random there is often a pattern to it. Rock paper scissors is a good example of people trying to be random.
You hear men lament on how they don't understand women or women go on about some man that didn't do what normal people should have done ... they just aren't seeing the pattern or don't have enough insight or information to be able to read it.
A logical person may not have enough empathy to see why an emotional person did this or that and vice versa.
Many actions can be fueled by past experiences and issues. Jenny was rude and off putting to Jack for no reason .... Jenny didn't realise that it was because a guy with dark hair and a leather jacket broke her heart at the age of 19 and that subconsciously Jack reminded her of him due to his appearance .... also Jenny was a bit of a cunt anyways.
Feet firmly planted, hands on hips to make himself seem larger ... aye, yer about to be shot.
Most of human communication is non-verbal, you can get body language cues without having to know the reason but once you get the cue then look for other things to back up whatever you suspect. Folded arms can mean they are defensive/adversarial or are submissive and are trying to make themselves a small target or maybe it's just fucken nipply out.
Leaning can mean not interested, legs folded can mean relaxed, feet under your chair can mean submissive or respectful, the body language needs to be read along with the situation. At a Doctor's waiting area you expect relaxed (if they have all day) or agitated people especially when the Doctor is running behind.
Groups of people too, who is standing closely to whom and is it within arms reach? (intimate/comfortable range) or at arms length which is normal everyday social range or are they moving away every time a person approaches? Who is dominant and who moves to the back and tries to look small?
You may not get all the answers when reading people but if you keep at it you may get spookily good at it. You can go up to a group of people and ask, "are you dominant?" or "so, you two are a an intimate couple right?" .... but I'd not advise it as you may be telling them something they didn't want others to know.
What Old Knudsen calls people that walk with earbuds in or walk while looking at their phones .... victims.
Most people don't pay attention to what is going on around them, most people don't even look up at the sky for fucks sake.
Body language cues can tell a person engrossed in what they are doing to someone pretending to be engrossed. When you multitask you have to keep going back to the task and may do it slower or you may do it faster to make up for not paying attention. A person fixed on doing a task will usually lose all sense of awareness to their environment.
You can tell who is watching you while pretending to talk into their phone, their conversation isn't fluid and maybe they have to think about what to say, their attention is divided. You can either do one thing well or two things badly.
Two types of people that are aware of their environment. law enforcement/security etc and the bad guys. People turning round to see who is behind them isn't normal civvy behaviour and so they can stand out like that.
Of course once a cop sees something they may become too focused and thus lose situational awareness just like that.
I saw a movie in which a house was being staked out, they could tell something was up whenever a guy came outside his head would do a sweep of the perimeter ... he had the training.
There is no reason that once you complete your daily tasks that you do a 360 look at yer environment. Continue to do that everywhere. A purse snatcher is less likely to go for someone who seems aware of their surroundings and just looked round at them while they were walking down the street.
Fantasize about Old Knudsen in the shower for fucks sake.
Any other anomalies than just a group of Middle eastern men should be observed and your concerns reported. Nervous Middle Eastern men in a huddle at the food court who all keep patting the back packs by their feet and getting silent when someone passes.... Yeah that seems suspicious.
One quiet man with a back pack can sit by the wall all day and never attract attention though.
It isn't the movies or what some Americans think their live would be like if they could carry a gun. If you have something to report then do it unless yer a rabid racist that watches Fox news as then yer judgement is already proven to be impaired. Otherwise get away ... the more distance the less deadly the attacker can be ... or hide and put a ton of stuff between you and them .... yer last option is to fight which is more likely to get you killed but no action at all can get you killed too.
Don't evacuate as that could have you heading towards the attacker, lock yourself in if possible.
Old Knudsen can use his training to help you survive this life thing but only if you listen. It's also important to listen to yer gut too.... but not about yon Tunnock teacakes yer fat gut says yes but yer arse says no.
This is obviously a gang of Mexican gang bangers. 
Twat or pussy thats yer choice, Cunty McCain will win.
Evil that can fit into a hand bag.
