On All Souls Day, November 2:
piously visit a church or a public oratory
recite one Our Father, the Creed, and one Hail Mary for the Pope’s intentions.
receive Holy Communion
go to Confession within 7 days; and,
have no attachment to sin, even venial sin.
Besides the indulgence which is specific to November 2, you can always say a short prayer for the dead. A simple prayer that our family adds to the end of the blessing before meals is "May the souls of the Faithful departed, through the mercy of God, Rest in Peace, Amen." This can be done especially in November, but throughout the year as well.
And another well known devotion and prayer would be this, dictated by Our Lord to St. Gertrude the Great to release 1,000 Souls from Purgatory each time it is said:
"Eternal Father, I offer Thee the Most Precious Blood of Thy Divine Son, Jesus, in union with the masses said throughout the world today, for all the holy souls in Purgatory, for sinners everywhere, for sinners in the universal church, those in my own home and within my family. Amen."