One of the questions I ask JWs before discussing anything with them is:
"What facts, evidence or otherwise would you consider as proof that Jehovah's Witnesses are not the true religion?"
I thought it was unfair to simply ask that of them so I figured I'd answer a similar question:
"What facts, evidence or otherwise would I consider as proof that Jehovah's Witnesses have the truth?"
Here's my answers...
http://www.youtube.com/watch?v=Mg0AYlFOZJs
If you'd like to add your own please feel free, or just comment on mine.