Just to show those who doubt I can post on-topic :)
The best way to reach a Jehovah's Witness is to talk with them right after they experience a large positive adjustment in their self-regard:
A) talk with them after they have engaged in some non-religious activity that requires thought, commitment, and rewarding hard work - attaining a degree, a certification, or reaching a level of expertise in a field. When we have accomplished something substantial, we become more confident and more sure of our own worth as an individual, and thus are more ready to make a choice that would require us to exist as individuals.
B) talk to them after they fall in love (note that this only works if their relationship is not "in love" with them because thay make a good trophy in the cong, but an actual romantic relationship. It doesn't have to be the love of their life (statistics say it's probably not) but again, being in a romantic relationship can dramatically increase our self-regard (even if only temporarily - strike while the iron is hot!)
We build beliefs, habits, and automatic reactions two ways - repetition (like the JWs) and by emotional involvement (also the JW's, but negatively - through fear of rejection). Your best results will be attained when communicating with someone who feels strong and capable - otherwise, they retreat into the shell.
But how do I get someone to this point, you ask? I don't think that you do... we all get there when we're ready, not when others want us to be ready.