No wonder this is the most favorite passage for many people. It's got a ton of great things to say.
The word for born "again" is usually the word for "above". Nicodemus understands it to be "again." Otherwise, his questions wouldn't make sense.
Moses in the wilderness with the snake is the only Old Testament that Jesus references in this discussion with the Jewish religious leader. It is perfect! (Numbers 21:8-9).
John noted very clearly, "You can't receive anything unless it has been given you from heaven." This is as clear a statement of the need for grace as there is in the whole Bible.
John's response, "He must increase and I must decrease," comes after a disciple feels sorry for him. The pharisees had taken note that Jesus was surpassing John! "Lots of water" indicates that the baptism was by immersion. Otherwise, it wouldn't make any sense to say that.
God did not give the Spirit to Jesus with any limits! That is the key to much of His life.