In the 21st Century it is imperative that you know how to protect yourself. This is no longer an option in our society but a duty. A physical altercation is the worst case scenario. Even if you have the upper hand it still can play out really bad for you. We are fragile creatures and small blows to very specific areas can shut the lights out for good. The best bet is to become a master of avoiding danger and altercations at all cost.
One of the best ways to do this is to be aware. If someone is following you there is a reason. Depending on the setting you will quickly understand the reason. How can you be sure if someone is following you and your not just paranoid? Read this article and it will give you the quick answers on this topic.