A Guide to Plenary Indulgences
Visiting a Cemetery: An indulgence, applicable only to the Souls in Purgatory, is granted to the faithful, who devoutly visit a cemetery and pray, even if only mentally, for the departed. The indulgence is plenary each day from November 1-8; on other days of the year it is a partial indulgence.
Visiting a Church on November 2: A plenary indulgence, applicable only to the souls in purgatory, is granted to the faithful who, on All Souls' Day (or, according to the judgment of the ordinary, on the Sunday preceding or following it, or on the solemnity of All Saints), devoutly visit a church or an oratory and recite an Our Father and the Creed.
Praying for the Faithful Departed: A partial indulgence, applicable only to the souls in purgatory, is granted to the faithful who,
devoutly visit a cemetery and at least mentally pray for the dead;
devoutly recite lauds or vespers from the Office of the Dead or the prayer Eternal rest. (Manual of Indulgences, fourth edition, 1999)
Indulgence Requirements:
To gain a plenary indulgence, in addition to excluding all attachment to sin, even venial sin, it is necessary to perform the indulgent work and fulfill the following three conditions: sacramental Confession, Eucharistic Communion, and prayer for the intention of the Sovereign Pontiff.
A single sacramental confession suffices for gaining several plenary indulgences, but Holy Communion must be received and prayer for the intention of the Holy Father must be recited for the gaining of each plenary indulgence.
The three conditions may be fulfilled several days before or after the performance of the prescribed work; it is, however, fitting that Communion be received and the prayer for the intention of the Holy Father be said on the same day the work is performed.
The condition of praying for the intention of the Holy Father is fully satisfied by reciting one Our Father and one Hail Mary. A plenary indulgence can be acquired only once in the course of the day, a partial indulgence can be acquired multiple times.
If a visit to a Church or an oratory is required to obtain an indulgence attached to a particular day, this may be accomplished from noon of the preceding day until midnight of the particular day.
Source: The Manual of Indulgences, fourth edition, 1999
(Enchridion Indulgentarium)