They will rarely - if ever - discuss doctrine. They tend to focus on the areas of personal attack, or attack 'controversial' topics.
Control
Control
Control
Control
They do not get to choose the topic.
You do.
If you don't, they will just lead you on an insane dance around every awkward question you ever ask.
Every time they answer your question ...pause and ask yourself ... did they really answer the question that I asked?
If they didn't, accuse them of whatever trickery they used to weasel their way out of answering a genuine question from their own son/brother/dad/whatever and restate your question without rephrasing it. They have to feel guilt for trying to fool you/dishonesty/double standards etc..
Make them read a 'difficult' article to you and explain it. You shut up except to guilt them for any subterfuge.
If you need a specific publication and you can't Google up a PDF, or all the links are dead, ask for it giving the full name and year of publication.
You should get a WTCD if you don't already have one. If you quote from that, your JW hasn't got any sane way of denying they said it.
A good example from the WTCD is "The Nations Shall Know That I Am Jehovah - How?" from 1971. Page 216, paragraph 9. Get your Dub to read it to you and explain it, then keep him honest.
9 Shortly, within our twentieth century, the “battle in the day of Jehovah” will begin against the modern antitype of Jerusalem, Christendom. The ancient “soil of Israel” pictures the realm in which Christendom has operated. It pictures the standing and relationship that Christendom has claimed to occupy with God by means of his “new covenant” of which Jesus Christ is the mediator. Now is no time for anyone in Christendom to rely on any righteousness on the basis of his own merits and to boast of his own self-righteousness. Jehovah’s “sword” of warfare will cut off from this position that Christendom’s clergy claim for her all religionists who depend upon her having an acceptable standing with God.