Situational awareness, we all have the means to do it. I still practice it almost anywhere all the time. I take it on the road, not for bad guys so much as just looking out for plain lousy drivers, vehicles with unsafe loads etc.
As for bad guys, whats a crook look like? could be anyone. Based on looks is a bad way, use behavior. Learn what's not the norm for the time and place.
Trying to educate my wife on what's a "dirt bag" and stay away from those. At home she caught on fairly well. On a trip to our beach house, we drove over to the harbor. She sees this old dirty guy walking away dressed in old rain pants and tee shirt. She says "They have bums down here too!" Me, no dear that's a fisherman. He has a boat docked and might be walking home after a long morning out in the ocean.
In Idaho we were visiting a small farming community, looking for property to buy. We stopped at the only gas station/store. She asks are those 2 guys bums? They got out of a beat-up ford pickup. They were really dirty, wearing the standard blue jean overalls. Me, no dear, those are farmers.
Put those 2 situations back in our neighborhood and yes they would likely be bums.