There simply seems to be nothing overly special or procedural about what Jesus is saying. In fact, most of what he says to Nicodemus is just gibberish.
The author of John has a predicament. The Jewish scripture makes all the promises to Abraham's get, but Christians weren't all former Jews by any stretch. He needs to change what counts as a seed of Abraham. It is not your physical heritage that matters, but your spiritual one.
So he shapes things a little/lot - and suggests that only those that come from heaven can return there. Therefore, though you have a physical body that came from earth, you have a spiritual part that can be 'born' in the light of heaven. Abraham's seed is all those that are born from heaven.
The bit about Nicodemus being confused is clearly a narrative crutch for John to express his views which I believe may have been resolving the problem of God's chosen people, and the Gentiles that came to follow Christ. Especially since this conversation is probably less confusing in the Aramaic it was presumably in. Strangely 'anōthen' is almost always translated as 'from heaven' or 'from the beginning' rather than 'again'. The only reason to use again is because of the context of Nicodemus' reply - but this relies on Nicodemus and Jesus using Greek in their discourse which is, of course, ridiculous. In John 3 it is translated as both
John 3:31 writes:
He that cometh
from above is above all: he that is of the earth is earthly, and speaketh of the earth: he that cometh from heaven is above all.
There simply seems to be nothing overly special or procedural about what Jesus is saying.
OF course not, Jesus was the founding figure of a religion not a science!
It's all about subtly suggesting things and letting the reader connect the dots. As you can tell from this thread and a casual look around the world that there are almost as many ways to connect the dots as there are people to connect them: hence the perceived need for a strong centralised church. The broad strokes are easily discerned though: The notion is that there are two parts to a person, a body and a spirit.
The body is born of earth.
The soul, made of wind/gods breath/etc which may choose to be born of heaven.
The procedure for doing this is to hear testimony of the son of Man and to believe it.
If you don't believe it then you're evil and you're going to piss God off and clearly you lack the necessary wit and sophistication to perceive the Emperor's fine pantaloons.
™ Version 4.2