(This is my "Spiritual Food" entry for my parish's bulletin.)
From the Thursday on which Jesus Christ ascended into Heaven until the Sunday of the Jewish festival of Pentecost, St. Luke records that the Apostles were gathered together in prayer with Mary and over a hundred other disciples. (cf. Acts 1:1-2:1) These nine (Latin: novem) days marked the first novena of prayer in the Church.
Novenas are typically nine-day devotions to prayer for a particular intention, although there are also 30-day and "perpetual" novenas. Some consist of the same prayer for each day; some have a different prayer for each day. The Church established an official indulgenced novena for Pentecost, which asks for the gifts of the Holy Spirit. The Church also attaches an indulgence to novenas prayed before Christmas and the Immaculate Conception.
Novenas are not "Catholic superstition", so you should steer clear from novenas which guarantee to "work" if prayed X times a day and if you make X copies of the prayer. God and His saints are not "vending machines" and novenas, like all prayers, are meant to teach us perseverance in faith, trust in God, and acceptance of His will.