Points to consider:
John calls this miracle a sign. The sign, according to John, revealed his glory. According to O'Day and Hylen, the term glory is an Old Testament term for the manifestation of God's presence and power (e.g., Exodus 24:15-18; 34:29-35; 40:34-38).
The stewards knew there was some very good wine but they didn't know that it was there because of a miracle. The bridegroom knew less. Yet, the disciples knew that a miracle had occurred. And because of the miracle, they believed. Or, was it because they believed, that they recognized that the miracle had happened?
What about the stewards, the bridegroom, the guests? Were they ever able to see God's presence and power in their lives? How about me? How often do I recognize God's presence and power in my life?
Other signs in John include 2:12; 2:1; 6:26; 10:20.