The First Announcement
The first announcement of the Messiah's birth was given by an angel to some anonymous shepherds.
Luke 2:11 For unto you is born this day in the City of David a Saviour which is Christ The Lord.
Why shepherds? Why not to priests or scribes? Shepherds were really outcasts in Israel. Their work not only made them ceremonially unclean, but it kept them away from the temple for weeks at a time so that they couldn't be made clean.
God doesn't call the rich and mighty; He calls the poor and the lowly.
1 Corinthians 1:27 But God hath chosen the foolish things of the world to confound the wise: and God hath chosen the weak things of the world to confound the things which are mighty . . . . 29. That no flesh should glory in His presence.
The Messiah came to be both the Good Shepherd and the Lamb of God, sacrificed for the sins of the world. It was fitting that the good news about God's Shepherd and Lamb be given first to humble shepherds.