"Does anyway have any short pointers on dealing with a JW?"
Let me start by saying that there was a time in my life that I had to make a decision between becoming a JW and denying the deity of Jesus Christ or believing in His deity. I had started Bible college as a new believer a couple of months before trying to "rescue" someone from becoming a JW. It was both the most terrible and the best experience as a new believer. As we know God is able to make good come of all things. Whether it was all part of His plan or simply making best of my ignorance, it did serve to bring me to my knees and in utter despair to cry out to God for the truth. You see, there were 2 elders that were , unbeknownst to me, invited to the "rescue" meeting that I had agreed to. They had all sorts of questions - and the answers too - when I could give no reasonable apology for my beliefs. They could argue their beliefs, albeit erroneous, from Scripture when all I could do was to spout the "party line." All of this to say, be careful and be ready. You must be firm in your beliefs and understanding of the truth before going one on one with any heresy.
I actually used to, after much study (I would not allow any person except God to teach me what was true) and a year or two, begin to seek out and witness to JWs on the street. I would point out the typical discrepancies of belief between what they believed and what I knew to be the truth. Years later I felt it best to find a different basis for arguing. Now when I cross paths with a JW, or Mormon or whatever I remind them that Scripture from beginning to end teaches us that those that earnestly seek Him will find Him. Then I ask them if they can honestly say that that they have earnestly and diligently sought after Him, especially through prayer. I might give a short testimony of how I had to cry out to God to know the truth and that true to His Word He revealed Himself and the truth to me. I freely admit to them that one of us is wrong because we both know that we are different sides of the fence when it comes to doctrine. I cried out to God, could they say the same. Then I would simply encourage them to trust no one, not even me, but to go home and earnestly seek from God to know the truth because their eternity rests upon knowing truth and not believing a lie. I remind them that God is faithful to His promises to reveal Himself to those that diligently seek Him. They cannot argue against what I have then shared with them but must decide for themselves if they are going to go home and earnestly seek God or continue in their false beliefs. I have actually had some to thank me profusely for sharing with them. But of course the glory goes to God alone.
2 Chronicles 15:2 The LORD is with you when you are with Him. If you seek Him, He will be found by you, but if you forsake Him, He will forsake you.
1 Chronicles 28:9 If you seek Him, He will be found by you; but if you forsake Him, He will reject you forever.
Psalm 9:10
Those who know Your name trust in you, for You, LORD, have never forsaken those who seek You.
Psalm 14:2
The LORD looks down from heaven on all mankind to see if there are any who understand, any who seek God
Jeremiah 29:13
You will seek Me and find Me when you seek Me with all your heart.
Hebrews 11:6
And without faith it is impossible to please God, because anyone who comes to Him must believe that He exists and that He rewards those who earnestly seek Him.