Walking the local trail, street, in the store, sitting in your car, wherever. That sense you get when something isn’t right - listen to it. Take a second look, make eye contact, keep tracking whatever it is, and “...Be polite, be professional, but have a plan...”... you know the rest.
Don’t forget to keep an eye above. A few years back, a jogger was on a trail during a considerably windy afternoon and a large dead branch fell from an old tree, hitting her and ultimately causing her death. Threats aren’t always human.
Learn to inform your awareness, actively observe your environment and make it a habit.
Stay alert. Stay safe.