I use this Forum, alot. to see how to argue the bedst way:)
You will notice a difference between Narkissos' posts and mine. Nark writes from a scholarly point of view, I write from a JW point of view. Though I agree with what Nark says preaching truth to a JW is not always effective. I generally take the approach of undermining the accuracy of WTS arguments, without undermining the very fundamental JW view of the bible.
In this case Higher Criticism of the bible shows that Genesis was written by a number of people. As Nark shows, some scriptures mention YHWH right back to the time of creation. However, JWs dismiss Higher Criticism, so I generally approach JWs from the simple angle that Genesis 6 says God Almighty did not make his name known to Moses ancestors. Jesus did not use YHWH in the New Testament. Therefore the word Jehovah is not a criteria for salvation.