Two JW's came to my door. After bantering about various doctrines, I asked, "How is one saved?"
Appearing to be caught off guard, they responded, "By the life you live." Clearly they weren't prepared to answer this question.
I said, "In your 'Truth' book, a verse is quoted about Jesus, which says, "There is no other name under heaven by which man must be saved.""
Then I said, "And your church is based on the verse which says, "Whoever shall call upon the name of the LORD (Jehovah to them) shall be saved.""
Finally, I said, "Based on these passages, Jesus and Jehovah are one and the same, or there are two names that provide salvation."
They quickly gave an excuse to leave, and departed.
When encountering a JW, never let them divert you from Jesus to other doctrines.