Situational awareness. Always observe your surroundings. Act like you're carrying 100K in cash, through the roughest neighborhood imaginable. The key is to look for people who look like they might do you harm, intentional or otherwise, whether they are on foot or behind the wheel.
Plan reactions to threat situations that seem almost impossible. That way, if the seemingly impossible happens, you'll not be caught with your pants down. In addition to the mental, accesorize with the physical to the maximum allowed by your employer and your own capabilities.
I carry an orange vest, and when walking on the side of the road, hold my camera so that my toplight faces traffic, and leave it on. The natural motion as you walk kind of makes it a flashing warning to traffic. Be careful not to blind the drivers.
I also carry mace, a knife(or two) & heavy maglite, for dealing with trouble of the bi-pedal variety. I would carry a roscoe, but the company would rather send my wife a funeral arrangement for my grave side than allow me a fighting chance should a situation elevate to that level. But, the best solution is work hard not to end up in such a violent situation in the first place, which loops back around to situational awareness.
