Despite what some may believe, we are not called to prove that God exists. I believe that only God can prove this. We are instead called to give an account as to why we believe, namely, that salvation comes through Christ [1Peter 3:15, 16]. This, I believe, is a three part process.
First, the call of God must be on a person’s life. He or she must be filled with the power of the Holy Spirit of God and sent purposefully to spread the gospel, not randomly of his or her own accord [Acts 16:6-10].
Second, the Holy Spirit must work between the parties and lead the encounter in the way the Spirit sees fit. The person spreading the gospel must be humble and open to the flow of the Spirit of God [Acts 16:6-10].
Third, the person or people being preached to must be open to the Word of God and the work of the Holy Spirit, even if they don’t know of the Holy Spirit, their minds should be receptive to the message, in order to receive the seed and have it watered occasionally by other believers and or other circumstances [Acts 8:26-39]. If a person is to receive Christ and be saved, the above things must occur.
For more insight check out Words of Inspiration Inspired by the Word of God at: http://www.larrywood.weebly.com