Sign#1 - Water to Wine (John 2:1-11)

John's purpose in relating the seven signs is to lead us to faith in Jesus Christ, to believe that He is the Christ, the Son of God, and that by believing we would find life in His name (John 20:30-31). How does Jesus' more-or-less secret miracle, turning water to wine at a wedding feast contribute to John's purpose? Why is this the "First" sign that John gives us?