It is fairly obvious that the main method of evangelism in the first century was oral. Paul and other missionaries proclaimed the Gospel to people who “hear the word of God.” Since travel was limited in the ancient world, the missionary had to travel to places where the most people will hear the message. It is doubtful if Paul’s mission would have done very well at all if he had stayed in Antioch and taught people who came to hear his message. Since he was called to preach the gospel to the Gentiles, he needed to travel to large cities where he could find public venues for his proclamation of the Gospel.
As Schnabel points out, this need for maximum exposure means the market place, where people were accustom to hearing various speeches (Paul the Missionary, 37). Traveling orators frequently turned up in the agora, gathered a crowd and made philosophical speeches. For example, Dio Chrysostom describes the Cynics as hanging around public places and publicly mocking other philosophers:
…still these Cynics, posting themselves at street-corners, in alley-ways, and at temple-gates, pass round the hata and play upon the credulity of lads and sailors and crowds of that sort, stringing together rough jokes and much tittle-tattle and that low badinage that smacks of the market-place. Accordingly they achieve no good at all, but rather the worst possible harm, for they accustom thoughtless people to deride philosophers in general, just as one might accustom lads to scorn their teachers, and, when they ought to knock the insolence out of their hearers, these Cynics merely increase it. (Orations, 32.9)
When describing orators in Tarsus, Dio Chrysostom says:
Accordingly men come forward to address you who are both empty-headed and notoriety-hunters to boot, and it is with mouth agape for the clamour of the crowd, and not at all from sound judgement or understanding, that they speak, but just as if walking in the dark they are always swept along according to the clapping and the shouting. (Orations, 34.32)
For Paul, this may have been a problem since he consciously separates himself from the orators. Because of the nature of his mission he must go to the market place and speak to crowds when possible, but he does not want to be confused with the others working these crowds. In 1 Thess 2:3-8 he makes it clear that he does not use elements of rhetoric (flattery, etc), but rather the Gospel is successful because of the power of the Holy Spirit. Because he proclaims the gospel Paul runs the risk of appearing as an orator, but he works very hard not to be confused with them.
But Paul did not go everywhere – there is no record of his preaching in a pagan temple. He seems to avoid them altogether in his mission. In Lystra, he may have been in the temple precincts since the priests of Zeus try to make a sacrifice to him (Acts 14), and in Athens he preaches on Mars Hill near the altar to the Unknown God. Neither case went the way Paul would have liked. If Paul had gone into a temple or temple court, how might the have addressed any crowd which might have gathered?
Here is the problem for the application of Paul’s mission to present mission efforts: How do we to people “where they are at” while making it clear that we are not “where they are at”? Are there lines which cannot be crossed if the Gospel is to be genuinely given?