@village at this moment most growth is indeed in latin/south america, africa, asia. And indeed there is still growth in the US and some other western countries. But also the situation in western countries we should see in the right perspective. The last 5 decades Europe/U.S are becoming secular at high speed. Church attendance and membership is dropping ultrafast. Churches are closing down etc etc. In that kind of environment JW's hold ground or even manage to grow slightly. That on itself is significant.
Informal witnessing is a great way too. But lets not forget that JW's do not believe that they'll have to convert people. They just give a witness and believe that it is Jehovah who makes sure the desireable things of the nations will find their way into the kingdom halls.