Although we don't live in a war zone and there is clearly no need to become paranoid, I thought that it would be good nonetheless to share a few tips to help reduce the chances of becoming a victim in the street. Here is number 1:
#1 Be aware of your surroundings. Awareness (and trust in your instinct) is the number one factor that contributes to upholding safety.
Again, we don't live on a battlefield so I won't refer to these sophisticated, colour-coded, "levels of awareness" that are advertised by many security experts. What I am talking about instead, is the kind of "soft" awareness we develop when driving a car. You know, looking right-left, a glance at the mirror, etc. So, on foot, in the street and particularly at night, it does not hurt to have a look, from time to time, over your shoulder to see who's behind you, and to pay attention to your surroundings as you would do while driving your car. Then, if something is not right, your instincts will tell you.
In our daily, hectic modern life, two things greatly reduce our level of awareness: headphones and mobile phones. As the increase of accidents involving pedestrian wearing headphones shows (see here and here), with headphones on you might not hear the car or the bus or the train, you certainly won't hear the bike, and it is fair to say that you won't hear anything either if anyone is coming in your back. So, for these reasons you should consider taking off your headphones in certain circumstances or areas.
Mobile phones are another distraction. Worse, they tend to attract thieves (see this article about phone snatchers in the The Guardian and this CCTV footage). So, when you're talking to people on the phone in the street, think about using the headset. Many of us text while walking or waiting for the bus making ourself an easy target for phone thieves (see this example). CCTV footages show that phone snatchers are usually on bike and that they go back and forth until they find a target. They approach their victim from the back or the side but always towards an exit route often crossing the road. So, if walking try to stay alert to your surroundings and not completely immersed in your texting (that will also prevent you from being run over by a car). If waiting for a bus try to position yourself in a way that would make it harder for a guy on a bike to grab your phone from your hand without having to stop.
Many people feel safer chatting on the phone while walking at night and/or deserted streets/areas. The problem with this is the distraction and the low level of awareness it creates. The problem can be turned around simply by describing what you see to the person you're talking to. Think of it as a game. No need to go into details, just a simple descriptions of the street/houses/cars would help keep your level of awareness to a decent level.
While we are at it with mobile phones, it is worth mentioning apps, such as ReactMobile, that turn your smartphone into a safety device which gets you help with the touch of one button, sending alert through text, email even Twitter or Facebook account, to pre-set contacts including the police. Using your phone GPS, the app is able to indicate your precise location to your contacts. See this recent article for more information and a comparison of the 5 most serious products. I haven't tried any of these apps but it might be worth testing.
I hope this will help - Feel free to share your experience or your tips.