Get them to read Matthew 24: 29-31 and ask them whether this has been fulfilled yet(they will say 'No, it is future') Then get them to read Matthew 25: 28-30 and ask them the same question (they will also say 'No, this is future'). Then ask them whether Satan is presently ruler of the world (they will have to say 'Yes' according to John 12:31 and 1 John 5:19) Then ask them who Jesus shares his world rulership with (they will say "only 144,000 persons taken from earth). Ask them if they can see any contradictions so far.... They may try and fall back on Rev 12 to try and prove there is a 'short period of time' (so far 92 years) between when Jesus becomes King and Armaggedon. If they do then pointedly ask them "please prove to me from the bible precisely what or whom Jesus been ruling over since 1914"? They will ummm and errrr and say they will call back another time to answer your questions.....which they never will.
Class-Questions for JW's
Simple, non threatening questions are the best way of reaching a JW because it shows you are interested but puzzled.
Here's one re: Blood.
Let's assume that it is true that the Bible forbids the use of blood in transfusions. Why is it permitted then to use certain fractions/solutions/derivates made from blood? The Bible doesn't split blood up in it's components, so are these then not human made rules?
You could use Adam and Eve as an example: they were forbidden to eat the fruit. Now would they not have been punished if they decided to eat just a tiny bit (a fraction), or if they cooked the sirup out and ate that?
Those are simple but thought provoking questions. Any householder could come up with these questions so they do not raise red apostate flags...