Ask them if they think they’re perfect. Almost all people I have talked to know they ain’t. They already know what that means with respect to God. What they do not know is that Jesus is God Himself.
While most people are willing to admit that they aren't perfect, most of them don't think they need a savior for it. They think they're good enough, that their good works will outweigh the bad.
Without that internal conviction of sin, which only the Holy Spirit can give, they won't see their need for Him.
And they need to be told the righteous requirements of the Law. And they need to be told of the consequences of breaking it.
THEN the Holy Spirit can convict them.