A small percentage go through life acutely aware of everything that goes on around them; and prepared to take action if necessary.
When I started looking into getting a CCW permit, I found that it was a little more involved than simply jamming a pistol in your pocket. With great power comes great responsibility. The lives of innocents and loved ones around you are not instantly saved by the simple fact that you happen to have a gun on your person. You need to do more. Much more.
You have to be aware of how you appear and are perceived by other people.
You have to be perceptive of the people around you.
For most people, this means living in conditions.
In my eyes, there are only 4 conditions. This is kept simple for a reason, the differences between the four needs to be clear.
Condition White (or green)
This is the lowest condition; this is sheeple mode. Very little attention is paid to your surroundings, and you are very relaxed. Some people argue that you should never be in condition white, and that the lowest you should go is some other condition between yellow and white. To those people I say, you must relax some time. Being in a constant state of alert and readiness will take its toll on you physically, and mentally. Don't do it. All that I ask about being in condition white is that you are prepared to escalate at a moment's notice. This is mainly a mental thing, but some equipment preparations are required.
If I'm sitting on the couch, watching TV or computing, I'm at condition white. But, I'll usually have my EDC knife on me or have a pocket knife on the coffee table in front of me (it's full of crap anyways), and I'll always be mentally ready to toss the computer, and bolt to the bedroom where firearms can be retrieved. Having this in the back of my mind doesn't really escalate my condition (I think), but not having it in my mind makes me unprepared.
What doesn't fit?
To me, condition yellow should be maintained whenever you are out of your house or around people you don't know. You are attentive to the strangers around you, how they're acting, what they're doing, what they're looking at, where they're going, and so on. At first this seems like a daunting (if not impossible) task, but once you get used to how the floating sheeple act in the areas you frequent, non-sheeple or people doing non-sheeple actions will we surprisingly easy to identify. This heightened state of awareness will likely net you a few people to keep an eye on. 99% of the time, these people will not be a threat of any kind, but since you're keeping an eye on them, you will be prepared should you be wrong. You just have to constantly ask yourself; "Whom here does not fit?"
If I'm walking through the mall, my eyes are constantly moving across the crowd in front and I'm constantly glancing behind me. Scanning the clothing, faces, body language, and movements of the people within 75 feet of me and my party. If someone is milling around or appears to be waiting in an odd area, I try to note where they're looking. Are they glancing expectantly at the parking structure, waiting for friends? Or are they scanning left, right, and behind them to make sure no one is coming? Is their body language tense or relaxed? If they don't fit, I probably won't deviate from my path or change the way I act; but I will be watching them.
Condition orange is the realization that something is wrong. Odd or furtive movements by someone you're watching can escalate you to condition orange. Unfortunately I don't have a precise explanation of what defines condition orange beyond "Something's Wrong" (maybe that's a good thing). Sometimes condition orange can be attained by something as innocuous as a bad vibe you get from someone. Yellow and orange are very similar, but one important differentiator is that condition orange is the first stage of readiness and possible action. At condition orange you need to begin becoming physically and mentally prepaired to take action, and you possibly take avoidance action.
If while walking back from a resteraunt to our car I notice someone has been with us for a few turns, and is acting strange/differently, I will go to condition orange. At this point, I may place my thumb into my pocket and pinch my knife in a thumb and palm grip without removing it, but my primary concern is to keep from having to go to condition red. Since I'm beginning to suspect this person of bearing me ill will, I can no longer treat him like any other person (though he may still be). Hence, I am unable to take any overt action but must find a way to confirm or deny my suspicions. I may stop my party and feign forgetting something for long enough for him to pass. Someone with malicious intent may realize he has been spotted and walk on as if he was just another innocent sheeple wandering after his car. If this person sees us stop, and ducks behind something so we don't notice him following us or stops to innocently talk on his phone, it's time to go to condition red. If he was maintaining a distance, and begins to rapidly close the gap, it's time to go to condition red.
Possible threat, take action.
Strangely enough, condition red is not the final condition. Condition red is for confirming or avoiding the possible threat any way necessary. The final condition is the fight for your life and the lives of others, and need not be a condition. If you've made it to condition red correctly, your attentiveness will likely be rewarded by not having to go to the final condition. Once you've correctly identified a possible threat, you have the advantage of the first move. Usually this is finding/notifying security, calling the police, or if those are not viable actions, taking evasive action or turning the tables. If you've noticed someone acting strangely, and have positively identified them as a possible threat, fetching security will keep you from having to confront anyone. Likewise, if you're walking home, and notice some possible threats, you can call the police and ask that a unit drive by and talk to you for a short while to scare the threat away. Note that you MUST positively identify a possible threat before you do any of these actions. If you call the police and say that someone's walking behind you, they won't care. If you tell them you've walked in a circle, and have confirmed that someone is following you, they will (should). The last two possibilities are more dangerous. Taking evasive action can include ducking into a safe area (preferrably a room or building with lots of people), or just flat-out running (only if you've already called the cops or know where to run). There are better ways to deal with this than running, be smart about thinking up safe areas, don't rely on simply outrunning your possible threat. Note that if you start running and they give chase, you have a clear escalation to the final condition. Turning the tables is the last resort, as it is simply a confrontation. You turn around, step aside, and stare at your possible threat to let them know you see them and are ready for them. They may walk on, or they may take the chance on trying to take you in a ready state. This should usually only be tried when you have the advantage of numbers. This is NOT recommended. You can usually call, seek, or notify the authorities without letting your threat know that you are doing so. Your advantage is that you get the first move.
Remember that in this condition, you must be very careful NOT to corner yourself. If you were walking to you car or your home, you MUST go elsewhere, or pretend to be unaware in safe areas long enough for the authorities to arrive!
Remember that nothing is confirmed! At this condition it's VERY likely this person bears you ill will, but it is still possible for innocents to cause this condition! Preemptive attacks are assault and you WILL be arrested!
The most important thing about the conditions is not how well you identify them, but how cleanly and appropriately you switch between them. When your suspect is not making it clear if you should escalate, try to think of an action you can take to either confirm or deny the escalation without confrontation or letting him know you are aware of him.
Some people live with conditions but don't carry; some carry but don't live in conditions. Just because you don't have a weapon doesn't mean that you can't live in conditions or that conditions will help you and your loved ones stay safe.
Example of how conditions can help in a possibly bad situation.
Followed walking home.
Jake finished feeding his friend's dog, and started the 5 block walk home to get ready for his date. Jake was at condition yellow, and after a block-and-a-half he noticed that a couple of guys 50 feet behind him matched a couple of his turns. "No big deal," he thought "lots of people walk here." He walked on, but was alert of his surroundings, and aware of the two behind him. After they matched a few more of his turns, he began to worry. "I think they might be following me, but I have to be sure I'm not just being paranoid!" Jake spotted a coffee shop, and walked in to look around and see if they passed. After a few minutes he walked back out and casually looked where they were as he turned to continue his walk. They were there, talking to eachother and gesturing at a nearby car. When he resumed walking, they slowly began behind him. Condition orange. From here we will take a few journeys to possible conclusions based on Jake's actions.
Jake decided to walk in a circle along populated streets to make sure they were indeed following him. As he made the last turn he peeked over his shoulder to see if they followed. They never appeared. They realized that he walked in a circle, and knew they had been spotted. After losing the element of surprise, they moved on to easier targets.
Jake picked a populated corner, and stopped to look at a newspaper in a coin-operated newspaper dispenser. When he did, he turned his head and made eye contact with the two briefly, before pretending to continue reviewing the paper through the plastic window. The two walked up, crossed the street, and walked on. They knew he saw them, but couldn't make a move on the crowded street corner.
Jake walked in the circle mentioned in the first possibility; this time, they kept following him. Now he was sure they were following him. Condition red. He casually reached for his cell phone, and called 911. "911, what is your emergency?" "Two guys are following me, I think they're going to rob me. I walked in a circle to make sure and they're definately following me." "What is your location?" "I'm walking North on Main, I just passed 42nd, and I'm wearing a brown jacket and blue jeans." "We'll send a unit by, keep walking straight." Half a block later a police car pulled up next to him, and called to him. He turned to talk to the cop, and as he did, he saw the guys behind him had crossed the street and changed direction.
The police did not arrive, and Jake was afraid they were going to realize that he was wise to them. Jake picked another crowded street corner, and turned around. He removed his hands from his jacket pockets, and stared at them. They hesitated slightly, and continued walking. "What are you looking at?" One of them said snidely as they passed him, and crossed the steet.
The police did not arrive, and Jake was afraid they were going to realize that he was wise to them before the police made arrived. Jake looked around, and now found himself without a crowded street corner to use. He knew he would have to make the first move before they did since they outnumbered him. He also knew he shouldn't confront them since they outnumbered him. He glanced up and down the street and saw no police cars. When he returned his gaze foward, he looked down to the side and noticed in his peripheral vision that the two men had quickened their pace. He was losing the first move. He didn't want to confront them, but he didn't know the area well enough to run. He walked up some steps to the nearest alcove of an apartment building so he wasn't visable to the men. He heard their pace quicken. He turned to face the street, and put his hand behind him. He heard the men slow as they approached the alcove and come into view. He glared at them as they came into view, looking into the alcove for him. They paused, looked at his face, looked at his hand behind him on the small of his back, turned, and walked on. Shortly after, the police arrived and were nice enough to give him a ride to his apartment.
Had Jake walked home in a blissfully ignorant condition white, he might have found himself beaten in an alley, or the victim of a home invasion robbery putting his loved ones at risk. As we could see Jake could avoid the potential situation a number of ways without going to far as to pretend he was armed. None of this would have been possible had Jake not been aware of his surroundings.
The problem living with conditions.
If you make the decision to live your life in conditions, there really isn't any going back. You can either be aware of all things around you, and perpetually prepaired, or you can't. Living in conditions can be a source of headache for you and possibly your loved ones. Had I been in condition white in this situation, everything would have happened the same way, and everyone would have been fine. The contant awareness and (yes, I'm going to say it) paranoia can be a wear on you physically and mentally. When I was in Vegas, I wasn't used to how everyone acted, and I had a tough time identifying the sheeple. It was a strain just being there, around so many people.
Does everyone have to live in conditions?
Of course not. And I certainly wouldn't think poorly of you if you decided not to. Even if your condition white sense of security was shattered by an act of violence, you can still choose not to live in conditions. The simple fact is that most citizens can go their entire lives in condition white with no problems.
Some people don't have the capacity to live in conditions. However, those who DO have the capacity should think very carefully about the people who depend on them for safety.
For more information on this topic, I HIGHLY recommend reading Xavier's post Recognizing Threats.