Jesus said, "Verily, verily, I say unto you, Except a man be born again, he cannot see the Kingdom of God" John 3:3.
"That which is born of the flesh is flesh; and that which is born of the Spirit is Spirit" John 3:6.
Peter wrote, "Being born again, not of corruptible seed (Adam) but of incorruptible, BY THE WORD OF GOD, which lives and abides forever" 1 Peter 1:23
Being born again is about receiving the Holy Spirit. We are all born into the world as lost sinners and need to be born again by the word of God. The word of God is the Gospel of Jesus Christ. Those that have been born again are those that have heard the Gospel and believe it. There is no other way to be born again. Catholics believe that they are born again by the works of the law. Do good works, obey the Catholic church and you will be born again. Calvinist believe that some how, at some time, God's zapps them with the Holy Spirit and they are born again. Both of these doctrines are false.
Paul wrote to the Galatians, "This only would I learn of you, did you receive the Spirit by the works of the law (because you did something) or by the hearing of faith?" (hearing and believing the Gospel) Galatians 3:2.
On the day of Pentecost when the Gospel first came into the world in the power of the Holy Spirit, thousands heard the Gospel, believed the Gospel and were born again, Acts 2:41. It was the preaching of the Gospel that gave birth to the New Testament church, Acts 2:41-47. The book of Acts is a book about how God in the power of the Holy Spirit is sending the "Good News" of his Son Jesus Christ into all of the world. The Holy Spirit transformed the lowly disciples into powerful preachers of the Gospel, Acts 4:13-22.
I was born again when I turned on the TV and heard these words, "But that thy blood was shed for thee". That is all that I heard. Billy Graham was giving the alter call. The Holy Spirit convicted me of my need for Christ and I became a Christian. That was 48 years ago, I have not been the same since. The change was that I became interested in spiritual things and less interested in things of the flesh. The transformation was slow but sure. The transformation is not what saved me, I was saved by the doing and the dying of Jesus Christ.
I have heard of people being born again by simply reading the Bible. A traveling salesman checked into a motel and found a Bible in the night stand that had been placed there by the Giddeons. He opened the Bible to the book of John and started reading it, just like me, the Holy Spirit convicted him of his need for Jesus Christ and he became a Christian. There are numerous accounts of people being saved in the New Testament. This is why Paul wrote...
So then faith comes by hearing and hearing BY THE WORD OF GOD (which is the Gospel) Romans 10:17.