A plenary indulgence is a complete release from the temporal punishment due for sins already forgiven (as far as their guilt is concerned). 

Conditions for a plenary indulgence: 

A. One must be baptized and in the state of grace. 
B. One must receive Holy Communion each time a plenary indulgence is sought.
C. One must go to Confession within approximately a two week period. A single sacramental Confession suffices for gaining several plenary indulgences.
D. One must have a disposition of mind and heart which totally excludes all attachment to sin, even venial sin, otherwise he can gain only a partial indulgence. 
E. One must pray for the intentions of the Holy Father, the Pope, preferably one “Our Father and one “Hail Mary,” however, any other pious prayer may be substituted. 
F. One must have at least a general intention to gain a plenary indulgence.
G. One must also fulfill one of the following suggested spiritual works:

     - At least a half hour of adoration of the Blessed Sacrament, 
     - or family or group Rosary, 
     - or private Rosary before the Blessed Sacrament,
     - or at least a half hour of pious reading of Sacred Scripture, 
     - or walking the Stations of the Cross in a church or with properly erected display of the Stations. 

Conditions for a partial Indulgence: A partial indulgence removes part of the temporal punishment due for sins already forgiven. 

The constant conditions for a partial indulgence are:

A. One must be baptized and in the state of grace. 
B. One must have at least a striving intention to cut one self off from all attachment to sin. 
C. One must have a general intention to gain an indulgence. 
D. One must fulfill the action prescribed in one of the following three general grants of indulgences: 

     - Offer up to God one’s trials in fulfilling one’s responsibilities and/or raise one’s mind in humble prayer; 
     - or give oneself or one’s goods as a charitable act to assist people who are in need of spiritual comfort or instruction and those who are in need of material assistance (donation of time and resources to the Church are, therefore, indulgenced); 
     -or voluntarily deprive oneself of what is lawful and pleasing, such as fasting, giving up dessert or a favorite TV program, while maintaining a positive attitude.