Begin by asking him to read Revelation 1:8.
“I am the Alpha and the Omega,” says the Lord God, “Who is, and who was, and who is to come, the Almighty.”
After reading this verse together, ask him the following question, “Who is the Alpha and the Omega?” He will respond by saying something like, “Well, it says right there, the Alpha and the Omega is the Lord God (or Jehovah God in their translation).”
Next, ask him if he will read another passage of scripture with you, and ask him to read Revelation 22:13.
“I am the Alpha and the Omega, the First and the Last, the Beginning and the End”
After reading this verse with them, ask him, “Now, who exactly is the Alpha and the Omega, the First and the Last?”
He will probably respond by saying something like, “We just saw who the Alpha and the Omega, the First and the Last is, he is the Lord God (or Jehovah God in their translation).
Lastly, ask him if he’ll look at one more passage with you, and read Revelation 1:17-18.
When I saw him, I fell at his feet as though dead. Then he placed his right hand on me and said: “Do not be afraid. I am the First and the Last (stop here and ask again, ‘who is the First and the Last?’). I am the Living One; I was dead, and behold I am alive for ever and ever!”
After reading this last passage of Scripture, ask him, “So, when exactly did the Lord God (or Jehovah God in their translation) die?”
Most Jehovah’s Witnesses will just look at that passage in bewilderment, for you have just shown them conclusively, even from their own translation, that Jesus is the Lord God (or Jehovah God). If you want to demonstrate this reality even further, read with him Revelation 22:13 & 16, where the Alpha and the Omega says, “I, Jesus, have sent my angel to give you this testimony for the churches.”