You can use the same basic principles when you talk with someone who has doubts about the Bible. Find out what he actually believes and what topics may interest him.
فَٱطْرَحْ عَلَيْهِ أَسْئِلَةً لِتَعْرِفَ بِمَ يُؤْمِنُ بِٱلضَّبْطِ ،‏ وَأَيَّةُ مَوَاضِيعَ تَهُمُّهَ .‏