Pray for your dead, and for all those in Purgatory, by starting this novena today and ending on the eve of the Feast of All Souls (November 1st).
O God, the Creator and Redeemer of all the faithful, grant to the souls of thy servants and handmaids departed, the remission of all their sins; that through pious supplications they may obtain the pardon they have always desired. Who livest and reignest with God the Father in the unity of the Holy Ghost, God, world without end. Amen.
For daily meditations to go along with the prayer, check out this site: All Souls Novena.