Improvise! When in a new or potentially dangerous situation, keep an eye out for items that you could use in a physical encounter. Things as simple as a handful of coins, or a glass of liquid can be used to temporarily blind your opponent, give you the upper hand and allow for a quick escape. Remember nothing is out of bounds when your safety is truly threatened.
Always be aware of your surroundings and the people in them. Predators often look for those who are easy targets. Those who are inattentive (or may be distracted by things like loud music in headphones; yeah, you know who you are...) are much more likely to be victims of a violent encounter. Keep yourself safe, and Stay Alert!