Well, as my posts and my links suggest, I think this is largely an exercise in futility. However, if you are intent (as I can tell you are) in going through with this, here are some suggestions.
I think you stated that this person is not an active witness. Like a christian who does not attend church regurlarly but still believes in the Bible and God, he or she may envision a 'perfect family life' that involves regular church / meeting attendance, mutual studying of the scriptures, and family prayer. Both the witness and the christian may harbor this hope for the idealic family within their respective religions. If either the christian or the witness feel that his or her religion is right and/or the other's religion is wrong, prepare for a lot of disappointment as it will be hard to shake the faith of either one of them.
Think about it, sure Christ Jesus was not born on December 25th but the typical christian sees nothing wrong with celebrating the first advent of Christ around the holidays and for many of them adds to the meaning of this time of year. The witness, on the other hand, sees this as wrong since it is based on a false premise. Likewise, the witness knows that Watchtower does get a few things wrong and may be wrong about things today, but the witnesses are good people trying very hard to serve Jehovah through an imperfect organization and that does not make them all that bad. At least that is the reasoning of the witness but the christian, on the other hand may wonder why the witness is so hard on outside religions when looking at their blemishes while simultaneously giving their own religion a pass concerning its own imperfections.
In the cases of both the witness and the christian, if neither one of them is very active in their chosen faith, they are probably holding this idealic view of their individual churches' teachings while recognizing that they just need to work on themselves to attain this 'perfect life.' The life that will probably not happen until after they get married, settle down, have kids, and THEN want to get more involved in their faith. If this describes either you or that witness in the slightest, prepare for a lot of disappointment unless either one of you is willing to give up your cherished beliefs (and I am assuming that you have a belief) and come together somehow. This is the voice of experience talking.
So let's say you manage to extract this person away from his faith in the Watchtower and the Jehovah's Witness teachings. Then what? Do you expect that he will embrace Christianity? Some might, but judging from the posts I read on this board, the words that my wife says when she is truly examining things, and from the words of one of my co-workers who was once raise a witness but is not one today, the most likely path for this individual is extreme skepticism that will most like lead to him becoming an agnostic leaning atheist. After all, if he believes that most christian churches are wrong and later discovers that his own church is wrong, how can he possibly prove that any one of them is right? As Terry pointed out, there are NO signed original writings of the various books of the Bible, there are only copies of copies. Add to that the fact that the collection of books that currently make up the Bible were all chosen by religious leaders over the centuries coupled with the fact that not all Bible canons are the same will ultimately lead anyone who is seeking the truth to wonder what exactly it is. The truth is, most people who have accepted a 'religious truth' cannot handle the truth.
Good luck to you, and feel free to post your progress with this individual as we will all be happy to critique your position and his most likely responses based on Watchtower teachings. However, I believe that unless he sees the dishonesty and double standards in this religion for himself, you are not going to get very far in cracking his JW armor. He is trained to ignore outsiders when they say things that attack their faith.
