ROME -- Italians have an expression for things that happen rarely, like running into an old school friend who lives far away. They’ll say they see the person “ogni morte di papa” or “every death of a pope.” 

With only four conclaves in the past 35 years there’s good reason for the expression, despite the fact that Benedict’s surprise resignation may force the phrase to change to “ogni cambio di papa”  or “every change of a pope.”

Though the events are few and far between, I’ve had the pleasure of being here the last three times the white smoke went up. And the election of Pope Francis feels reminiscent of the heady excitement surrounding the election of another outsider: Karol Wojtyla as Pope John Paul II.

Zany charm of a crowd of strangers
The first time I saw the white smoke I was just 16 years old, the editor of my high school newspaper at an American school here in Rome.

It was October 16, 1978, and it was the second conclave in just a few months, because the newly elected John Paul I had died after only 33 days in office. 

St. Peter’s Square was not as well lit as it is today. Only the church’s façade and the Sistine Chapel roof chimney were illuminated. The shoulder-to-shoulder crowd of almost 100,000 stood in a chilled darkness, sustained by an excited, Christmas-like anticipation of the announcement of a new pope. There’s something quite unusual, a little zany and inexplicably charming about standing in an enormous group of strangers, waiting for an arcane smoke signal to reveal a new leader.

The smoke finally appeared on that October night and there was a rush to interpret whether it was black or white. With a history of spotty results when it comes to ballot burning, there was room for doubt, but it ultimately turned a solid white and a thrill ran through the crowd. The anticipation built even more as we waited for the first appearance on the balcony, and the question “Who will it be?” crisscrossed the crowd in a dozen languages.

Slideshow: The election of Pope Francis

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Cardinals from around the world gathered in the Vatican to elect the next leader of the Roman Catholic Church.

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The Roman Catholic Church made history that night, electing the first foreign pope in more than four centuries. The red velvet draperies trembled and parted to bring forth a vibrant, youthful Polish cardinal. He immediately charmed the crowd in stumbling Italian, and then went on to radically transform the papacy with intercontinental travel, a constant television presence and a historic moral challenge to the Soviet Union’s harsh rule of Eastern European nations behind the Iron Curtain.

After high school and during college I worked for several of the American network news bureaus in Rome. Pope John Paul II was almost killed by a Turkish gunman in St. Peter’s Square in 1981, and I spent most of 1982 working for ABC News. In June of that year, I flew on my first “papal plane” when the pontiff visited Britain.

Satellite television and videotape had just come of age with John Paul II’s election, and the Pole’s long pontificate would rise, thrive and fall under the unblinking eye of the constant camera lens. For people who had known only one pope their whole lives, John Paul II would come to symbolize Catholicism: both stubborn and frail, often charming but also uncompromising.

Transitional, not transformational
The death of John Paul II in 2005 was mourned by millions. I returned to the Vatican for NBC News in 1996 after many years working in the United States and covered the last decade of his papacy.

Like most of my fellow Vatican watchers, I knew the Polish pope would be an impossible act to follow. Still, I hoped the cardinals would go for a bold choice over a safe one.  

Benedict was not that bold choice. But clearly the cardinals felt the church would benefit from a transitional figure, rather than a transformational one like John Paul II.

The white smoke came quickly that time, on the third vote after just a day and a half, and the excitement in the square was shared with cellphones in the age of the Internet. 

The election of 78-year-old Joseph Ratzinger, a full 20 years older than John Paul II at his election, would shift the image of the papacy to a staid, conservative and bookish one.

Many believe resigning was the most courageous act of Benedict’s entire papacy. It took a lot for someone who loves the trappings of Catholic conservatism as much as he does to break with 600 years of tradition, but Benedict did it, making way for one more puff of white smoke.

A swift surprise
This latest conclave also lasted a mere day and a half, a surprise in itself. Unlike the last one, where Ratzinger went in a clear favorite, this time there was an open field, no top contenders, and for the first time in history, not one but two Americans on the short list of possible popes.  

Courtesy Stephen Weeke/ NBC News

NBC News Producer Stephen Weeke walks with American Cardinal Timothy Dolan in Vatican City recently.

I now work out of San Francisco but came back to Rome to help TODAY with this conclave. After working all day at our live location overlooking the Vatican, I made it through the rain and crowds into St. Peter’s Square with minutes to spare before the smoke appeared.

The white smoke poured out of the chimney, with the force and color of something bellowing from a steam-engine locomotive -- there was no ambiguity this time. The crowd went crazy in the age of smartphones and social media, and basically crashed the local cellular network.

I waited for the announcement with other Americans, excited at the prospect of witnessing the arrival of an American pope. When the red drapes revealed a 76-year-old Argentine, I was initially a little disappointed. But the cardinal of Buenos Aires didn’t take long to change that feeling. 

When the new Pope Francis bent down to ask the crowd to pray for him, before he would bless them, I was moved. This man's humility seemed genuine, palpable and extremely public. Its effect on the crowd was immediate. 

Since then he has broken the mold in half a dozen ways. Refusing the papal limo and riding the bus back after his election with his fellow cardinals. Refusing the gold cross and keeping his iron one. Refusing the red slippers and keeping his clunky black walking shoes. Refusing a prepared speech and speaking off the cuff.

By naming himself after Saint Francis of Assisi, a beloved figure whose radical embrace of poverty reformed an ailing and corrupt church 800 years ago, the pope has already telegraphed that he is open to change.

It's high time the world had a pope with a common touch and a flair for the unscripted. Francis is already reminding a lot of us of the young John Paul II. I’m glad I was here to see his white smoke. 

Stephen Weeke was NBC News' Vatican producer from 1996 to 2005. He is now based in Northern California. 

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When the College of Cardinals convenes Tuesday to choose a pope, it will revive a centuries-old tradition — cut off from the world by an oath of secrecy and doors that close with a firm and final thud.

In a ritual that has been described by participants as solemn and moving, the cardinals will gather in the Sistine Chapel for their conclave, a word drawn from the Latin terms for "with" and "key." They will vote, four times a day after the first day, until they settle on a leader for the world's 1.2 billion Roman Catholics.

In many respects, the ritual is unchanged from the rules Pope Gregory X instituted 800 years ago. But this time, there's a wild card: The previous pope, Benedict XVI, is still alive, and while he won't be in the room, he will probably have an indirect say in the outcome.

Benedict spent just seven years as pope but appointed 67 of the 115 cardinals eligible to vote on his successor. The rest were appointed by his predecessor and theological soul mate, Pope John Paul II. Benedict also made changes to the voting rules that could keep the cardinals working long past the four ballots it took to elect him in 2005.

"It takes as long as it takes. No one wants to rush this," Cardinal Daniel Di Nardo, the archbishop of Houston, told reporters this week. While he spoke, Vatican workers were preparing the chapel for the gathering — closing it to visitors and installing anti-bugging devices and the stove where the cardinals' ballots will be burned to produce the black or white smoke that tells the world how they're coming along.

Locked up in the Vatican

However long it takes, the cardinals will be locked inside the Vatican, with no newspapers, no TV, no radio, no Twitter or Facebook.

During the day, they will deliberate inside the Sistine Chapel, beneath Michelangelo's breathtaking "Creation of Adam," with its famous depiction of God and Adam touching fingers.

At night, they will bed down in the Casa Santa Marta, which John Paul II had built in 1996. It's relatively modest but a dramatic upgrade from what the cardinals were provided before then — cubicles furnished only with cots and washbasins, with but one bathroom per 10 people.

Slideshow: Pope Benedict XVI's departure

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Pope Benedict XVI delivered his final audience Feb. 28, 2013, in St. Peter's Square as he prepared to stand down.

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Usually, the dean of the College of Cardinals presides, but the current dean, Cardinal Angelo Sodano, is 85 and disqualified from the voting, which is limited to cardinals under 80. So Cardinal Giovanni Battista Re, the prefect emeritus of the Congregation for Bishops, will be in charge.

Custom and conclave rules fashioned over centuries mean the cardinals have assigned seating, with the prime seats going to two "cardinal bishops" — the senior Rome cardinals who are younger than age 80 and therefore eligible to vote.

Then come the four patriarchs of the Eastern Catholic churches, the middle-ranking "cardinal priests" who make up the bulk of the college, and the most junior members, the "cardinal deacons."

"It does look quite dramatic, all of the cardinals dressed in scarlet sitting around," said Cardinal Cormac Murphy-O'Connor, former president of the Catholic Bishops' Conference of England and Wales, who took part in Benedict's election in 2005.

Then somebody says extra omnes: Everybody out except the cardinals.

"That's a very dramatic moment, because the door is shut — there's a thud," Murphy-O'Connor, who is too old to take part this time, told the BBC in a long interview for its radio documentary series "Witness" last month. "I remember looking around at the other 114 cardinals and thinking to myself, 'Well, one of us will be going out with a white cassock on.'"

Ballot after ballot, day after day

Once locked in the room, the cardinals will take a collective oath of secrecy. That's followed by a roll call in which each cardinal, with his hand on the Bible, individually swears: "And I, (name), do so promise, pledge and swear. So help me God and these Holy Gospels which I touch with my hand," according to John L. Allen's book "Conclave: The Politics, Personalities, and Process of the Next Papal Election." 

Allen, Vatican correspondent for the National Catholic Reporter, is considered one of the world's foremost experts on the church. His book, published in 2002, is an encyclopedic chronicle of how things work when the cardinals gather. Much of what else is publicly known about the process comes from the Vatican's Code of Canon Law and history and apostolic letters on the election of the pope issued in 1996 by John Paul II and in 2007 by Benedict XVI.

When the voting finally begins Tuesday, there will be one round of voting in the afternoon, followed by two every morning and two every afternoon until someone gets two-thirds of the votes.

Each cardinal gets two or three ballot papers, inscribed Eligo in summum pontificem ("I elect as supreme pontiff"). They're encouraged to disguise their handwriting and to fold the paper twice to prevent eavesdropping.

Then each cardinal walks up to an altar that stands before Michelangelo's turbulent "Last Judgment." After kneeling in a brief moment of prayer, he recites in Latin: "I call as my witness Christ the Lord, who will be my judge, that my vote is given to the one who before God I think should be elected." He then slides his ballot into a chalice using a large circular plate.

Three cardinals chosen at random count the ballots; three others chosen at random check their work. The cardinals can keep their own tallies, because each vote is read out before it's threaded with a needle and string; at the end, they're all gathered by the strings and tied together in a knot. Assuming there's no winner, the session's second round of voting begins immediately.

Twice a day, after the morning and afternoon sessions, the ballots are burned in a special stove.

That's how the masses outside know how things are going. If there's no new pope, the knotted-up ballots are treated with damp straw or a special chemical so that they produce a black smoke. The dramatic appearance of white smoke — signaling a winner — is produced by using a different chemical or by leaving it out altogether.

Technically, the cardinals are supposed to keep their own counsel, but many accounts over the decades make it clear that extensive debate and discussion goes on during breaks and in the residence.

A (relatively) new way of doing things

 Benedict's election was unusually quick, coming after only four ballots. More commonly, the balloting takes a few days, and because of a change Benedict instituted in 2007, there's the potential for a long conclave this time.

Benedict was elected under rules stipulating that after about 30 ballots, depending on how many votes are taken on the first day, the cardinals could choose to drop the threshold for election to a simple majority.

Benedict threw out that stipulation, meaning a two-thirds vote will be needed for all of the ballots. After 33 or 34 ballots, and occasional one-day breaks for prayer and reflection, the election is narrowed to the two leading vote-getters — but even then, Benedict ordered, the winner has to get two-thirds.

Many "Vaticanisti" — the pundits and journalists who obsessively follow the political goings-on of the church — predict that this change will result in a compromise pope, with the leader in early balloting ultimately fading.

Eventually, someone will be chosen, at which point the senior cardinal will ask the winner, "Do you accept your canonical election as Supreme Pontiff?" If he says yes (accepto), he is the pope, just like that. The new pope will then declare his papal name. 

"Then he goes out," Murphy-O'Connor said. "There's a papal tailor outside with three cassocks, white cassocks — large, medium and small — and then after 10 minutes or so he comes back and he's put in the middle and we all go up and kiss his ring.

"It doesn't matter how you voted, whatever. He's the pope now," Murphy-O'Connor added. "It's very dramatic, it's very moving, and it's very faithful."

After the white smoke appears — historically triggering extended cheers from the thousands gathered outside — a senior cardinal will step onto the balcony of St. Peter's Basilica and declare: Annuntio vobis gaudium magnum. Habemus papam. ("I announce to you news of great joy. We have a pope.")

The new pope, whoever he is, then appears before the throng and performs his first official public act. It is a simple apostolic blessing called Urbi et orbi ("to the city and the world"):

May the Holy Apostles Peter and Paul, in whose power and authority we have confidence, intercede on our behalf to the Lord.

Through the prayers and merits of the Blessed Mary ever-virgin, of Blessed Michael the Archangel, of Blessed John the Baptist and of the Holy Apostles Peter and Paul and of all the saints, may Almighty God have mercy on you, and with your sins forgiven, may Jesus Christ lead you into everlasting life.

May the Almighty and merciful Lord grant you indulgence, absolution and remission of all your sins, time for a true and fruitful penance, an always repentant heart and amendment of life, the grace and consolation of the Holy Spirit and final perseverance in good works.

And may the blessing of Almighty God, and the Father and the Son and the Holy Spirit descend on you and remain with you always.

Related:

• Riots, revenge and royal rigging: A history of controversial conclaves
• 'Jesus Christ with an MBA'? Cardinals' differing hopes for next pope
• Full coverage of the papal abdication from NBC News