You don't need a black belt in karate to lessen the chances of being a victim. Prevention goes a long way. Melissa Soalt, a self-defense trainer, suggests imagining how you would do the following things in a situation that could be dangerous:
Project strength, not vulnerability. Assailants "are masterful at sniffing out fear," Ms. Soalt says. A tentative gait, averting your eyes and backpedaling all telegraph fear. Walk purposefully, "taking up more space in the world."
Stay focused. Survey all that's around you. Use your peripheral vision. Instead of staring at the key as you open the car door, look at the reflection in the window. Don't let the element of surprise work against you.
Set physical boundaries. A stranger approaching for directions or a cigarette may be testing you. Don't let him get closer than 2 1/2 arms-length. Make sure you can see his whole body at all times.
Your voice is a weapon. Firmly state: "That's close enough. Step back." Don't look away. Keep you voice and body language congruent.
If he doesn't back off:
Don't be afraid to make a scene. Pull a fire alarm. Pick up a rock and throw it through a window. Assailants don't want to be seen.
Your car is a weapon, too. Keep doors locked and windows up. Keep scanning the surroundings, ready to accelerate if need be. Use the car mirror as "eyes in the back of your head." If you stay far enough away from the car in front to see its rear tires, you'll always have space enough to get away.