A good way to talk to someone who does not believe in God is to start by asking them for their reasons for not believing in God. That way you will possibly discover the topics you need to discuss. Different people will have different needs; there isn’t an approach that will fit every situation. This is partly Paul’s point in 1Cor. 9:19-24:
{19} …though I am free from all, I have made myself a servant to all, that I might win more of them. {20} To the Jews I became as a Jew, in order to win Jews. To those under the law I became as one under the law (though not being myself under the law) that I might win those under the law. {21} To those outside the law I became mas one outside the law (not being outside the law of God but under the law of Christ) that I might win those outside the law. {22} To the weak I became weak, that I might win the weak. I have become all things to all people, that by all means I might save some. {23} I do it all for the sake of the gospel, that I may share with them in its blessings.
Paul adapted himself to the situation he was in, depending on the needs of the people he was preaching to.
Whatever approach you take, 1 Peter 3:15 has advice we need to follow:
in your hearts honor Christ the Lord as holy, always being prepared to make a defense to anyone who asks you for a reason for the hope that is in you; yet do it with gentleness and respect
When we talk to people about the gospel we need to do it gently and with respect towards the other person.