Never let your gas gauge get below one quarter of a tank. Be aware of your surroundings. Walk with confidence. We are all potential victims. If we give the would-be criminal numbers 1 and 2, he will find number 3.
Personal awareness is truly the key to prevention.
Also, attach a photograph of your vehicle. Never leave keys in unattended vehicle. When you're in it and when you leave it. Keep valuables out of sight, locked in trunk. Carry a spare key on your person.