Jehovah Witnesses really don't work in debate mode, because they are groomed to not believe a word you say (like Mormons) but the only way to really win them is building a friendship. One ex-Jay Hov I Bible studied later commented to me that he would often try to get me to loose my patience, but I would only laugh, and keep the discussion going. What really impacted him was me wanting to be friends instead of wanting to clone him into my brand of religion. Sure scriptural proofs were given, but through it all there had to be a genuine want to see the individual as a life long brother. I look at it this way, whether they be Eastern Orthodox or Jay Hove Witnesses you have to get them to see Jesus, not you, the real Jesus and when they see that, then they open up and listen, with full attention.
Then, there is always praying them through to the Holy Ghost. I have done that with many in a Bible study, Jay Hoves, Mormons, even a starchy Church of Christless, and it was something to see, oh, and hear.