The biblical way? I don't know what you mean here. In this day and age with the explosion of the population and as big as the world is now evangelism can sprout out into different avenues of approach. there are now technologies that we have now that evangelists never dreamed about during the first century. God had created these technologies, or for their potential, and we should use them for the benefit of proclaiming the Gospel. Again, I'm not quite sure what you're getting at but that is what I would say.
Also, about these follow ups after crusades. The whole point of evangelism is not to get people to go to your church, it's to bring people into the kingdom of God. Whether these churches see an increase in attendance or not shouldn't suggest that people really weren't saved or had a real experience with God. What it does suggest to me is that the other offices of the Church are not doing their job. Evangelism is to proclaim the Gospel to the lost, it puts the word out, gives the message and that is all. I don't believe that the way we do evangelism today is the problem but that the other offices of the Church; the pastor, teacher, prophet, and apostle are failing to do their job.
EPH. 4:11-13, It was he who gave some to be apostles, some to be prophets, some to be evangelists, and some to be pastors and teachers, to prepare God's people for works of service, so that the body of Christ may be built up until we all reach unity in the faith and in the knowledge of the Son of God and become mature, attaining to the whole measure of the fullness of Christ.
All of the 5 offices of the Church have to work in concert with each other. If they don't, the work of the evangelist may result in no effect. If the evangelist does his job and many make a decision for christ then the other offices of the Church have to then do their part.
Think of the 5 offices of the Church as a well oiled machine when it works as Jesus Christ intended it to work. I think with what you've said shows not that we are doing evangelism wrong but that we don't have a well oiled machine in operation.