Between mentors and Reading books & magazines, and learning by doing, I was very gun savvy by age 18. When someone approached me at the range, I'd give them a minute to size them up. If they were obnoxious, I would tell them to mind their own business- then smile. They either walked off or smiled and visited. One old gentleman told me that I was wasting my time shooting my scoped Blackhawk at 100 yds. After pulling my target with a 4" 6 shot group, he asked to try it. Of course I let him and the old phart shot a 3" 100 yard group! We bonded that day and he let me shoot his Sako .17-.223. I KNEW what wildcats were so he was tickled.
Always give a person a minute before you decide what they are. Once identified, they can be dealt with accordingly.