If you are speaking to someone specific then I would first use the above points in pointing out that they really do have cultic behavior and ruling in the society. I then would perhaps shift the focus off of calling or defining 'what' they are ie: cult, religion, or
'truth' *smirk*. The point I would bring up is despite all the technical clasifications of a cult that they fulfill they main concern is that they are a cult in their beliefs as well. They are even further classified by many as a 'psuedo-christian cult' because they have cultic behavior and they are a false christianity. Perhaps take the focus off of clasifications and 'study' with them showing how their beliefs are not in the scriptures and therefore are not christianity-- If a JW really cares about God then it will matter to them if the Bible matches their beliefs or not. Sharing this info will not be easy or accepted by them easily but is just as important as pointing out their groups detrimental cultic actions.
If you are researching for yourself then the above applies too, just make sure you study the Bible to compare to their doctrines-- You will find that they are not scripturaly correct. They tend to manipulate people who have little to no knowledge of the Bible and indoctrinate them before they get a chance to read it for themselves--thus leading them to their own JW conclusions.
My 2cents Angie <><