I'd say the best way is to start thinking like a BG would. Watch how other people go through their day. Try and identify the risks they take, how you would attack them if you wanted to.

Sometimes I would think of who would be the easiest one on the platform to push off just as the train is coming by. Or maybe how easy it would be to dump some powdery substance on a pizza while waiting in line at the restaurant, or into someone's drink as I am walking by, without anyone noticing. Watching people walk under objects thinking what might happen if something came loose and it fell on them. In so observing others and their routines, you begin to condition your mind to recognize such hazards yourself. I also mark subjects around me as to who might pose the most likely physical threat based on profiling. It might not be politically correct, but I am not running for any office either. It is all about creating habits out of routine, of changing the way you go through your day. If you go through a war zone, you develop some habits very quickly.

It is easy for us in our insulated little worlds to relax and let our natural talents atrophy. Really, we are built to be functionally aware of our environment, but society erodes our instincts and alters our perceptions so that our skills become dull, our complacency becomes bad habits and ignorance. Pierce the veil once or twice, and I would almost gaurantee you will have a different outlook about your daily routine.