FaithfulWitness:
Do you have any ideas for simple questions I can ask, with sincerity, that might cause someone I know or meet, to start thinking critically?
In general, take the approach suggested above by jgnat. Keep things informal.
For JWs interested in logical analysis, you can take this approach: Get them to open their Bible to Jeremiah 25:12. Read the verse. What is the order of events? Do 70 years end before or after Babylon's king was 'called to account'? Because Babylon's king is called to account after the 70 years ends, the 70 years is not of exile, and it can't end after 539 BCE. Then send them here.