It's really about being aware of your surroundings. Also, I believe, the time of year. Little story:
There was this dead end street in my neighborhood, behind the local gas station, where everybody went to change their oil on their cars (behind a shopping center, near the post office). The neighborhood was considered relitively crime free. On one side of the street was a 15' wall with the shopping center lot above. On the other, a chain link fence closing off a vacant lot. I was there one evening, at dusk, finishing my oil change, with my head under my hood, when I became aware of 2 males walking down the street, beside the wall. Due to the wall, I could hear them talking. As they got closer I heard one say "let's take him out". Whoa. I'd been watching them out of the corner of my eye and when I heard this I moved around to the passenger side of my truck, opened the door, reached under my seat, stood up, and looked at them squarely, with my hand hidden. They started to purposely ignore me and hurried on by. This being the Christmas shopping season, I'm sure I was about to be mugged. If it wasn't for the urinal that I kept under the seat, and my awareness of my surroundings, I'm sure I would have been. Story not over. I moved my truck around to the front of our apt. building, on a busy street, and parked. I was sitting in the passenger seat, with the door open, logging the oil change in the little notebook I carry, when I became aware of another person walking down the street. When he was about 30' away, he started to look around him, a lot, in every direction. Hmm. Seemed strange. I stood up, behind the opened door, again with my hand out of sight, and stared him down. He hurried down the street. Didn't need the urinal this time.
I'm sure I was reading their minds correctly (the 1st two I heard correctly), but I was tuned into my surroundings and diverted any confrontations. Keeping yourself at a hightened state of awareness, especially during the holiday season, is usually the key to safety on the streets. Never let them see both hands.