This is similar to a couple of your already wonderful tips. When Columbo starts talking about his wife, nephews, and other family, recognize this as a tactic to (a) delay you and/or put you off guard, and (2) give him time to process significant information with his "grey" cells while entertaining/distracting you with seemingly insignificant small talk.
Terrific post Joe. I particularly liked #4 "AVOID COLUMBO". That happens so often. I can think of so many examples where Columbo just shows up out of the blue to restaurants, parks, murderers homes, airports..etc. Why don't these people just keep their whereabouts to themselves.