The Church offers us different prayers that we can say every day of the week for the faithful departed. These are especially useful for offering a novena on behalf of the dead, or for praying during those seasons of the year (November, in the Western Church; Lent, in the Eastern Church) designated by the Church as times of fervent prayer for the dead.
Catholics pray this prayer on Saturdays for the souls of the faithful departed.
Saturday Prayer for the Faithful Departed
O Lord God omnipotent, I beseech Thee by the Precious Blood which gushed forth from the sacred Side of Thy divine Son Jesus in the presence and to the great sorrow of His most holy Mother, deliver the souls in purgatory and among them all especially that soul which has been most devout to this noble Lady, that it may come quickly into Thy glory, there to praise Thee in her, and her in Thee through all the ages. Amen.