Acts 18:3 KJV
And because he was of the same craft, he abode with them, and wrought: for by their occupation they were tentmakers.
I see three "venues" of witness used by the Apostle in the city of Corinth:
He reasons in the synagogue and persuaded the Jews and Greeks there.
I see this as working with those who have some knowledge of the Scriptures, but are not born again. It is apologetic work. The point is not to introduce them to doctrines they have never heard but to direct them as to what those doctrines mean. America is filed with people who know all about the Lord but do not know the Lord
He entered Justus' house and worked with the Gentiles there
This appears to be the work of introducing Gospel truths to those who have no concept of them. This is the case of the majority of people in the world. More and more it is becoming the truth of America. We now have generations of people who have no basic knowledge of the Bible.
He abode with and worked along side Aquila and Priscilla.
This is the least glamorous and exciting of the three. There are less thrills, fewer risks, and you won't get your name in the Christian periodicals when working with one couple. But I point out that of the three, only in this case do we see fruit that goes on to produce fruit. Aquila and Priscilla become very useful in the work of the Lord and their names pop up over and again in Scripture.
To be sure, the first two must be done. Sowing that seed, watering and tending it, must be maintained, and in large volumes. But the rewarding work; the work that produces the most refreshing fruit, will be the work that is done over the long haul.
I notice that Paul not only worked alongside of them, but abode with them as well. It has to do, not only with being a present testimony, but developing a personal relationship. I means that Paul did more than teach them and witness to them, he became close to them.
Christians must push themselves away from just relationships with other Christians and introduce themselves into other audiences and build relationships with lost souls in order to win them.