There is plenty of stuff on the Internet about the Jehovah’s Witnesses, including sites dedicated solely to exposing their false teachings. For this post, I’m just going to give you a primer about their teachings so you can readily see they do not witness for the true God of the Bible, but a God of their own making who has a false Christ for a son.
1. The Trinity. The Jehovah's Witnesses deny the Trinity, saying the word is not found in the Bible.
a. Jesus was originally the archangel Michael before being born. He was only a man while on earth and became Michael again. (The Watchtower, 5/15/69, p.307 and 12/15/84 p.29) He is to be worshiped as a "glorious spirit." Jesus was re-created vs. resurrected. (You Can Live Forever in Paradise on Earth, p.143, 145; The Kingdom is at Hand, p.259; The Watchtower, 9/1/53, p.518; et al) He is NOT God in the flesh.
b. The Holy Spirit is merely "God's invisible, active force." In Reasoning from the Scriptures, on p.381, they teach that the Holy Spirit “is not a person but is a powerful force that God causes to emanate from himself to accomplish his holy will.” They also teach, in Should You Believe in the Trinity, that the Holy Spirit is “a force that can be adapted to perform a great variety of operations.”
Christian response: There are a lot of words not found in the Bible, but our word “Trinity” describes what the Bible plainly teaches about God, Jesus and the Holy Spirit. Hebrews chapter 1 is excellent for demonstrating the superiority of Jesus over the angels. You might also point out that Rev. 22:8-9 says angels refuse worship - that worship is for God only, which demonstrates that Jesus can’t be an angel.
a. "The perfect justice of God would not unjustly accept more value than that of the thing to be ransomed.... It was the perfect man Adam that had sinned and so had lost for his offspring human perfection and its privileges. Jesus must likewise be humanly perfect, to correspond with the sinless Adam in Eden. In that way he could offer a ransom that exactly corresponded in value with what the sinner Adam lost for his descendants. This requirement of divine justice did not allow for Jesus to be more than a perfect man." (Things in Which It Is Impossible For God to Lie, p. 232). Herbert Kern, in the booklet How to Respond to the Jehovah’s Witnesses, points out that, “On the one hand, Jehovah’s Witnesses say that Jesus died for all mankind. Yet they limit the value of Christ’s ransom and belittle the immensity of His work of atonement. They claim that Christ was no more than a perfect man. So they teach that His atonement as the case of one perfect human life being given to redeem another human life. They maintain that Jesus gave His life as a ransom for Adam only.” (p.28)
b. Salvation is found only in the Watchtower organization. The Watchtower, 11/15/81, says, “come to Jehovah’s organization for salvation.” (p.21). The December 1, 1981 issue says, “unless we are in touch with this channel of communication that God is using, we will not progress along the road to life, no matter how much Bible reading we do.” (p.27). This is but a sample of their claim.
c. Works are necessary for salvation. “…to get one’s name written in that Book of Life will depend upon one’s works.” (The Watchtower, 4/1/47, p.204). “Parents who love their children and who want to see them alive in God’s new world will encourage and guide them toward goals of increased service and responsibility.” (The Watchtower 3/15/62, p.179) “We have to do more than merely accept the Kingdom message in order to be saved. We also have to preach it in order to show that we believe it. We are saved by more than just believing the Kingdom message with all our hearts; we must also publicly declare that Kingdom message to others.” (From Paradise Lost to Paradise Regained, 1958, P.249) The Watchtower society teaches that one cannot know if they have salvation in this life, because it also depends on their performance during the millennium.
d. Initially God’s Kingdom will be 1000 years. Paradise will be restored to earth and those resurrected will have the opportunity of gaining eternal life on earth. By the end of the first 1000 years every trace of unrighteousness will be removed and all mankind will stand as perfect creatures at the throne of God, who will then test their loyalty by releasing Satan and his demons. Those who remain loyal will be judged worthy of eternal life.
e. By misuse of Revelation, the Watchtower society teaches that only 144,000 people, a special class who have been “born again,” will enter heaven, while all other “saved” people will live forever on earth. This second class is known as the “Great Crowd” in Revelation. The opportunity to be one of the 144,000 ended in 1935, so Jehovah’s Witnesses now look forward to surviving the destruction of the rest of mankind at Armageddon and living forever on earth. Since the Jehovah’s Witnesses teach against the reality of Hell, the unsaved will be annihilated and cease to exist.
3. The Watch Tower Bible and Tract Society is God’s mouthpiece - the prophet on earth.
a. “The Watch Tower Bible and Tract Society is the greatest corporation in the world, because from the time of its organization until now the Lord has used it as His channel through which to make known the glad tidings.” (The Watchtower, 1/15/1917, p.6033)
b. “Is not the Watch Tower Bible and Tract Society the one and only channel which the Lord has used in dispensing his truth continually since the beginning of the harvest period?” (The Watchtower, 4/1//1919, p.6414)
c. “Jehovah’s organization alone, in all the earth, is directed by God’s holy spirit or active force.” (The Watchtower, 7/1/1973, p.402) The Watchtower society has made hundreds of false prophecies since their beginning. By the test of Deut. 18:22, they are proven to be not God’s prophet!
4. Other aberrations:
1. When God wages war against mankind at Armageddon, all but Jehovah’s Witnesses will be destroyed, with all other churches being destroyed first.
2. Absolutely no celebration of birthdays is permitted, not even sending a card.
3. Blood transfusions are not allowed.
4. True Christianity disappeared from the earth shortly after the death of the apostles.
5. Christ returned invisibly in 1914 to set up the Watchtower society.
6. The cross is a pagan religious symbol. Christ died on a stake.
7. Celebration of any holidays is strictly forbidden, being considered worldly.
8. No one can understand the Bible apart from JW publications.
Remember, do not chase the Jehovah’s Witnesses away when they come to your door, or it will reinforce what they have been told about them being persecuted for their faith. Invite them in and show them from Scripture that works don’t save. Also have them read Hebrews chapter 1 out loud and quiz them about Jesus not being an angel. There are many ways to get them off their rote presentation and arguments and plant seeds instead. They are deceived and Hell-bound, and need evangelization.