This just occurred to me.

John 2:1-10(NKJV)

On the third day there was a wedding in Cana of Galilee, and the mother of Jesus was there. 

Now both Jesus and His disciples were invited to the wedding. 

And when they ran out of wine, the mother of Jesus said to Him, “They have no wine.”

Jesus said to her, “Woman, what does your concern have to do with Me? My hour has not yet come.”

His mother said to the servants, “Whatever He says to you, do it.”

Now there were set there six waterpots of stone, according to the manner of purification of the Jews, containing twenty or thirty gallons apiece. 

Jesus said to them, “Fill the waterpots with water.” And they filled them up to the brim. 

And He said to them, “Draw some out now, and take it to the master of the feast.” And they took it. 

When the master of the feast had tasted the water that was made wine, and did not know where it came from (but the servants who had drawn the water knew), the master of the feast called the bridegroom. 

And he said to him, “Every man at the beginning sets out the good wine, and when the guests have well drunk, then the inferior. You have kept the good wine until now!”

How did Jesus mother know to ask Him to turn the water into wine?  He hadn't done any miracles yet.  If I had to pick an explanation I would suggest that it was at the prompting of the Holy Spirit. 

Now you may say wait a minute.  Don't we get the Holy Spirit after we believe in Jesus?  That would be correct.  But there are several instances throughout Scripture that tell of God giving the Holy Spirit to others before Jesus arrived on the scene, so there is precedent of this happening.