"If a Bible Christian knocks on your door and asks, 'Have you been born again?' perhaps the best answer would be, 'Yes, I've been baptized.' (Caution: Your answer may surprise your questioner.) Here's a strategy that may help you share about Baptism when someone's question has opened the door for discussion.
Open your Bible to Jn. 3:5-8 and share Jesus' challenge to Nicodemus: 'Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God' (Jn. 3:5). Highlight the context of this passage: In a previous chapter, Jesus' Baptism is recorded, which brings together the images of water and the Spirit (in the form of a dove) along with God the Father's recognition of His Son (Jn. 1:32-33; cf. Mt. 3:16-17). The passage immediately following Jesus' conversion with Nicodemus is the only place in the New Testament that records Jesus' baptizing others (Jn. 3:22). The overall context of the passage where Jesus speaks of the necessity of being 'born of water and the spirit' is Baptism.
Without downplaying our need for ongoing conversion, emphasize that this passage in Jn. 3 addresses the objective act of Baptism, rather than a subjective conversion experience. Then ask in all sincerity, 'When were you born of water and the Spirit? When were you baptized?'"
-Kimberly Hahn in the chapter "Born Again: What the Bible Teaches About Baptism" from the book Catholic For A Reason: Scripture and the Mystery of the Family of God.