First and foremost, it needs to be noted that being aware of one's surroundings and identifying potential threats and dangerous situations is more of a mindset than a hard skill. Because of this, situational awareness is not something that can be practiced only by highly trained government agents or specialized corporate security countersurveillance teams. Indeed, it can be exercised by anyone with the will and the discipline to do so.
An important element of the proper mindset is to first recognize that threats exist. Ignorance or denial of a threat -- or completely tuning out one's surroundings while in a public place -- makes a person's chances of quickly recognizing the threat and avoiding it slim to none. This is why apathy, denial and complacency can be (and often are) deadly. A second important element is understanding the need to take responsibility for one's own security. The resources of any government are finite and the authorities simply cannot be everywhere and cannot stop every criminal action. The same principle applies to private security at businesses or other institutions, like places of worship. Therefore, people need to look out for themselves and their neighbors.
Another important facet of this mindset is learning to trust your "gut" or intuition. Many times a person's subconscious can notice subtle signs of danger that the conscious mind has difficulty quantifying or articulating. Many people who are victimized frequently experience such feelings of danger prior to an incident, but choose to ignore them. Even a potentially threatening person not making an immediate move -- or even if the person wanders off quickly after a moment of eye contact -- does not mean there was no threat.
Much more HERE
Thanks to WiscoDave for the link