I have been listening to some lectures on evangelism and church planting by Roger Greenaway that were given at Calvin Theological Seminary.
In one of them he declares that small group evangelistic Bible studies are the most powerful and strategic method of evangelism and church planting. They are so flexible and so constantly used.
What a shame, he says, to ever send out a missionary or a church planter who has never had experience in sitting in on one, let along leading one.