While a novena is normally a nine-day [or nine hour] prayer, the term sometimes is used for any prayer that is repeated over a series of days. The Saint Andrew Christmas Novena is often called simply the "Christmas Novena" or the "Christmas Anticipation Prayer," because it is prayed 15 times every day (we pray five  each at breakfast, lunch, and supper) from the Feast of Saint Andrew the Apostle (November 30th) until Christmas. The First Sunday of Advent always is the Sunday closest to the Feast of Saint Andrew.
The novena is not actually addressed to Saint Andrew, but to God Himself, asking Him to grant our request in the honor of the birth of His Son at Christmas. You can say the prayer all 15 times, all at once, or divide up the recitation as necessary (perhaps five times at each meal).
Prayed as a family, the Saint Andrew Christmas Novena is a very good way to help focus the attention of your children on the Advent season.
Saint Andrew Christmas Novena
Hail and blessed be the hour and moment in which the Son of God was born of the most pure Virgin Mary, at midnight, in Bethlehem, in piercing cold. In that hour, vouchsafe, O my God! to hear my prayer and grant my desires, through the merits of Our Saviour Jesus Christ, and of His Blessed Mother. Amen.
(source: by Scott P. Richert at Catholicism.about.com)