It can be very difficult to study with Witnesses. It seems they always have responses programmed into their minds by the watchtower society, whether those responses are logical or not. Because of this, it is hard to get through to them, especially on the deity of Jesus Christ. So try to take an approach they will not be as ready for. Some verses I would show a Witness are verses that refer to Jesus as Jehovah/ YHWH. Whenever we think of the Great Name, “Jehovah (or Yahweh), we need to think of the whole Godhead/Trinity.
You can actually use the Witness’s own NWT when using these verses. (This is NOT an exhaustive list. I will be updating it as I find more!):
Genesis 1-3 Describe Jehovah God as the one who created all things, using the name Jehovah about 12 times. Jesus is described as the Creator of all in John 1:3 and Colossians 1:16.
Exodus 3:13-14 says that Jehovah is the “I AM.” Jesus says in John 8:58, “Before Abraham was born, I AM”
Deuteronomy 10:17 states that Jehovah is the Lord of Lords. Revelation 17:14 says the same about Jesus.
Deuteronomy 32 contains the song of Moses to Jehovah. Hebrews 1:6 applies Deut 32:43 to Jesus, where Moses says “Let all the angels of God worship Him.”
Nehemiah 9:6 describes Jehovah as the Creator of all things. Jesus is described as the Creator of all in John 1:3 and Colossians 1:16.
Psalm 23 calls Jehovah the Shepherd. Jesus calls Himself the Good Shepherd in John 10:11.
Psalm 68:18 Paul in Ephesians 4:8 quotes Psalm 68:18 about “Jehovah God” having “ascended on high” and applies it to Jesus having “ascended on high.”
Psalm 96:13 states that Jehovah will judge the world. 2 Cor 5:10 states that it will be the judgment seat of Christ that we all stand in front of. (also see 2 Tim 4:1)
Psalm 102 is a prayer to Jehovah. Verses 25-27 are quoted in Hebrews 1:10-11, where it says that the Father says this of the Son.
Isaiah 6:1-10 John in John 12:37-41 quotes from Isa 6:1-10 where Isaiah saw Jehovah of hosts’ glory, and states that it was Jesus whose glory Isaiah saw and spoke of.
Isaiah 8:13-14 Peter in 1 Peter 2:8 quotes Isaiah 8:13-14 about “Jehovah of hosts” who will be “a stone of stumbling” and “a rock of offense” to Israel, and applies it to Jesus who is “A stone of stumbling, and a rock of offense” to Israel.
Isaiah 40:3, Malachi 3:1 All four gospels state that John the Baptist’s preaching in the wilderness was the fulfillment of Isa 40:3, “Prepare … the way of Jehovah… our God.” But the “Jehovah God” who John prepared the way for was Jesus!
Isaiah 43:3 calls Jehovah the Savior. 1 John 4:14 and many other verses call Jesus Savior.
Isaiah 45:23 Paul quotes Isaiah 45:23 where Jehovah predicts that, “unto me every knee shall bow, every tongue shall swear” and twice applies it to Jesus, in Romans 14:11 & Philippians 2:10.
Jeremiah 9:24 Paul in 1 Corinthians 1:30-31 quotes Jeremiah 9:24 “but let him that glories glory in this … that I am Jehovah” and applies it to “Christ Jesus.”
Jeremiah 10:10 says that Jehovah is the everlasting King. The New Testament says that Jesus is King (Matt 21:5; Rev 17:14) and that His throne will be forever (Heb 1:8).
Joel 2:32 Both Peter and Paul apply Joel 2:32, “whosoever shall call on the name of Jehovah shall be delivered” to Jesus: “whosoever shall call on the name of the Lord shall be saved” (Acts 2:21; Romans 10:13).
Zechariah 11:13 In Zechariah 11:13 “Jehovah” predicts that the “price that I was prized at by them” [the "shepherds" of "the flock" - v. 8,12] was “thirty pieces of silver.” This was fulfilled by the Jewish religious leaders paying Judas “thirty pieces of silver” for betraying Jesus to them (Mt 26:15; 27:9).
Zechariah 12:10 In Zechariah 12:10 “Jehovah” (v. 1,4) predicts that “the inhabitants of Jerusalem … shall look unto me whom they have pierced.” This was fulfilled by Jesus being “pierced” by nails and a spear on the Cross (John 19:34-37; Revelation 1:7).