While the decision is a personal one and everybody has to do whats right for them. I strongly feel that the most good can be accomplished by those who stick it out as "faded" for as long as possible. I allows enough communication open that those who still talk to you will almost inevitably as why you don't go to meeting any more and boom you've got an in to drop just a few pieces of information on them they probably wouldn't have come across with open ears otherwise.
Choose your topic accordingly to whoever is asking as well. Some people its going to be U.N. association or the ARC. Others it will be doctrinal, "How can we not have Jesus as our mediator?" "How could there have been a first century G.B. if the "slave" wasn't selected until 1919, and that was in the middle of the gentile times when Jehovah had no earthly representatives?"