And when they heard of the resurrection of the dead, some mocked, while others said, "We will hear you again on this matter." So Paul departed from among them. However, some men joined him and believed, among them Dionysius the Areopagite, a woman named Damaris, and others with them. Acts 17:32-34

Of course the most desirable outcome when speaking to someone about Christ is that the person believes and follows Jesus, just as some did in Acts 17:34. Let me share an important evidence that a person has truly trusted Christ: Those who believed joined with other believers. This is always important. When a person comes to Christ, the person needs Christian fellowship in a solid church in which he or she can learn and grow in their new faith.

It is important to invite and urge new believers to get plugged into a church. Invite them to go to church with you. Offer to pick them up and actually bring them with you (if that is feasible). Just as new born babies need to be loved, nurtured, and cared for, new believers need the same kind of care and we can be a part of that as we help them get established in a Bible-preaching church.

As I said, an important evidence that a person’s interest is true saving faith, is that they join with believers in a church. It is exciting when we see this happen! But let us also beware that if a person expresses interest in the Lord, but ultimately refuses to unite with other believers, it is likely evidence that he or she hasn’t yet come to saving faith. Though that may be disappointing, don’t give up. Continue to speak to the person as though he/she is not saved—the person still may be in time!