A few years ago I spotted a couple one morning at a corner store getting coffee before they headed for service. So while they were in front of me in line waiting I asked them if they were headed "out in service"? You should have seen the looks they gave me since it was obvious from the hair on my chin that I wasn't a JW.
When they said "Yes, we are! We're pioneering this month, do you know what that is?" I said, "Do I know what pioneering is? I have Vacation pioneered, Temp. pioneered, Aug. pioneered, Reg. and Special pioneered". And I said it with a big smile, then walked out.
Back in the 70's I worked in Kentucky as a tour guide at Mammoth Onyx Cave. One time I was pretty sure this couple on the tour were JW's, so when I got a chance to talk to them after the tour I asked them where they were from, and they said Ohio. Then I asked them if they knew a man named Nathan Knoor? They started whispering then said, "We know a Nathan Knoor, but he lives in New York". Dub-dar!
I was a dub back then, so I asked them if they would come back to my home for dinner, they did, and we became friends.
I can spot dubs a mile away.