As a JW, we were taught that almost any conversation could/should be twisted adapted into a witnessing situation. We were continually urged to watch for "witnessing opportunities".
Someone says, "I wonder if we'll ever get out of Iraq", and you were supposed to say "That situation shows man's inability to rule. Do you think God will act to rescue mankind and assure good rulership?"
Someone at the car-repair shop asks why you brought your car there. You have a witnessing opportunity! You say something like, "You know, I've got to keep my car in top shape. I need it to go in a special ministry happening today...."
We were taught that as JW's, we were associated with the "Watchman" class (that's right, class) in Ezekiel. God told Ezekiel that as watchman, if he didn't warn the wicked one, he'd die too.
So as JW's, we were supposed to feel guilty if we didn't use each situation every day to embarrass ourselves by bringing up religion give a Kingdom witness.
Personally I disliked informal witnessing. I was more accustomed to the regular door-to-door ministry, although that wasn't natural for me either.
Did you like informal witnessing? Did you feel a bit guilty if you passed up informal "witnessing opportunities"?