Never try to tell a JW anything. There is a huge amount of information on the internet that you can show them. Don't tell them any of it and certainly don't show them any of it. They are trained not to listen. They are taught that Apostate websites are full of lies, you are trying to take them away from Jehovah and that you are influenced by Satan. So, what can you do???
Ask questions.
They are trained to teach, so ask questions. Ask in such a way that they feel obligated to answer. They are taught that they have knowledge that is neccessary to survive Armageddon, which is coming soon, and that it is their duty to share it. Use that to your advantage.
They are there to save you. You have a question. It is your question that is important because if they can't answer it with honesty and integrity, then they will never accomplish their God given mission.
Remember: You are not there to answer their questions. (They are not interested in your answers except to get you to make a mistake so that they can pounce on it.)
If you do have to show them something, try to make it something that they have in their own home. Try to stick to WT literature that they have in their possession or computer and books and articles that their literature has quoted from, and get them to read it to you and comment on it.
The primary doctrine is that the WT was selected by Jesus, in 1919, to be God's sole channel of communication to mankind in our day. As long as they believe that, the WT has full mind control. This is true even if they are studying, unbaptised, drifted or disfellowshipped. Everything the WT teaches is believed because of that doctrine. If the WT changed a doctrine tomorrow, they would believe the change, even if it is contradicted by the Bible or Jesus or Jehovah himself.
Your questions should be constructed to steer them towards stating their belief in that doctrine, but try not to put words in their mouths.
Some sample questions:
How do you know the WT is better than the Catholics/Evangelicals/Muslems/Mormons/whatever?
How do you know Jesus selected them?
When did Jesus select them?
Why did Jesus select them?
Can you show me an article that says that, please?
All the time asking, "How do you know ...?" type questions to steer them where you want them to go.
If they make a claim about the WT that you suspect is untrue demand that they prove it, or get them to read, to you, a WT article that you know contradicts them. NOTE: Do not read it to them!!!!!
Don't get sidetracked.
Red herrings are their favorite trick. They are trained to distract you from your subject and are experts at it.
Rule #1: Don't change the subject.
Rule #2: Don't let them change the subject.
Every time you read a disaster story about a conversation with a JW, the JW has had control of the subjects.
The tricks they use are mostly diversion tactics. They will:
Talk volumes about a related subject without discussing your question.
Ask a question about another subject.
Attack another church or their doctrine.
Attack your character.
Attack your motives.
JWs never stay with a subject that they are uncomfortable with, so, if one tries to change the subject, that is a very good indication that you should stay on that subject. Try to make them feel guilty for attempting to use these tactics on you. Use parallels to religions that they consider to be false if you can. If they have previously denegrated a religion for using the tactics they are using on you, point it out and pour on the guilt for it. Act offended that they should do such a thing to you. Guilt, guilt, guilt.
If a conversation reaches a stalemate, or one of you needs to go away to do some research, finish the conversation and walk away. Do not start another subject. Do not let them start another subject. They will always want to start another subject because they want to end the conversation feeling as though they have had a 'win' and they can do that if they can pick a subject that they are good at and you are not. It is time to go. Now. You can talk about sport or politics or itchy underclothing, but do not discuss another religious subject.
Once they have confirmed that they believe their primary doctrine, it is time to ask them how they know that they were selected in the year 1919 .... and that is another subject. It is an easy subject, but once again, it is all about knowing how to control the subject and not get sidetracked. They know how to take an easy subject and make it sound really complicated, so you must learn control.
Control, control, control.
I hope some of that helps.
Cheers
Chris