Conversion-based Church Planting - The Lydia approach

The apostle Paul began his church planting ministry in Europe after an initial conversion to Jesus Christ by a woman named Lydia (Acts 16:11-15). Conversion preceded church planting. In contemporary church planting ministry we tend to neglect calling secular people to follow Jesus in favor of initially starting a core group. Only after having a team of highly committed people does the church planting leader then begin to evangelize. The need of the hour, especially in Europe, is to return to an emphasis on conversion-based church planting. How can this occur? What are some old and new ways of reaching people with the gospel and then begin new churches with them as our core group?