Today marks the official start of the Saint Andrew's unfailing Novena. I, myself, have been saying this for several years now. Some of my prayers have been answered, others are still in the 'spiritual sandbox'.
You're supposed to say the following prayer 15 times a day, from November 30th until Christmas:
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 the piercing cold. In that hour vouchsafe, I beseech Thee, O my God, to hear my prayer and grant my desires, [here mention your request] through the merits of Our Saviour Jesus Christ, and of His blessed Mother. Amen.