A friend recently wrote me of his plans to visit the Holy Land and of his great excitement because it gives him the opportunity to gain plenary indulgences for his deceased parents during the pilgrimage.
When I asked him why he hadn’t tried to obtain one by his weekly holy hour or his family rosary, I was stunned by his response. He was quite irritated that I (supposedly!) had never mentioned this to him before. He thought this should be more widely taught.
Indulgences have had a checkered history, as Paul VI alluded to in his apostolic constitution  Indulgentiarum Doctrina directing that the Enchiridion Indulgentiarum, or handbook, of indulgences be revised following Vatican II. In acknowledging this, the pope also took the opportunity to beautifully clarify the teaching.
Through the communion of saints, the Church has a spiritual “Treasury,” which is primarily made up of the infinite value of Christ’s saving actions, but which also includes the merits of the prayers and works of the saints starting with the Blessed Virgin Mary. As members of the communion of saints, we continually contribute to and benefit from this treasury. But Christ also gave the Church the authority to dispense and apply these merits to the faithful at special moments.
Unlike material treasure, this “Treasury of the Church” can never be exhausted. One significant way the Church makes use of this spiritual benefit is through indulgences – a remission of the remaining temporal punishment due to sins already forgiven.
If you want an enchanting explanation of temporal punishment due to sins for your young children or grandchildren see “The Boy with the Nails” in Angel Food , by Reverend Gerald T. Brennan. For the rest of us, the Catechism explains it well:
Grave sin deprives us of communion with God and therefore makes us incapable of eternal life, the privation of which is called the “eternal punishment” of sin. On the other hand every sin, even venial, entails an unhealthy attachment to creatures, which must be purified either here on earth, or after death in the state called Purgatory. This purification frees one from what is called the “temporal punishment” of sin. These two punishments must not be conceived of as a kind of vengeance inflicted by God from without, but as following from the very nature of sin. A conversion which proceeds from a fervent charity can attain the complete purification of the sinner in such a way that no punishment would remain. 
In addition to the infinite graces available to us through the sacraments and the Liturgy, the apparitions at Fatima highlight the fact that being faithful to God’s law and the duties of our daily life provide us sufficient penance to expiate not only our sins, but those of others. On top of that, like whipped cream on a sundae, comes the gift of indulgences, which can be gained through particular actions or prayers as identified by the Church.
Partial indulgences add an equal remission of punishment through the intervention of the Church to that gained by the action itself. But plenary indulgences are amazing in that they remit all temporal punishment due to sins for a particular person.
It is possible to gain a plenary indulgence each day for oneself or for a poor soul in Purgatory, but not for another living person.
The steps to gain a Plenary indulgence are straightforward:
1. Be a baptized Catholic in good standing, be in the state of grace at least at the completion of the work, and intend – at least in a general way – to gain the indulgence (e.g. some versions of the morning offering include this general intention)2. Perform the indulgenced work or prayer3. Receive Eucharistic Communion for each indulgence (20 days before or after)4. Sacramental Confession (20 days before or after – since one confession suffices for a number of indulgences, monthly confession will satisfy this requirement nicely)5. Pray for the intentions of the Holy Father for each indulgence (Our Father and Hail Mary are suggested but we are free to choose – 20 days before or after)6. Have no attachment to sin, even venial
The condition that usually gives people pause is number 6. A document  issued by the Apostolic Penitentiary in 2004 describes this as being totally free from any desire to relapse into sin. This is reminiscent of Romans 7:15. It does not mean we have to be convinced we will never sin again, but simply that we absolutely do not want to sin in any way.
The most exciting thing about a plenary indulgence is that there are several ways to gain one each day: adoration of the Blessed Sacrament for at least one half an hour; devout reading of the Sacred Scriptures for at least one half an hour; the pious exercise of the Way of the Cross; or the recitation of the Rosary (five decades) in a church or public oratory, or in a family group, a religious Community, or pious Association.
Normally only one plenary indulgence can be gained each day but a second one can be gained at the point of death if you have no access to a priest. (This is a good time to make the general intention to receive that one!)
When you think about it, Catholics have an embarrassment of spiritual riches available to them. Through the Church we have access to everything that Jesus wanted to leave humanity. If we cooperate with God’s grace, making proper use of this largesse for ourselves and others, Heaven will not have to wait.