Dressed in a conservative, dark suit reflecting his position as an IBM executive, George Clements nevertheless played the responsive crowd like an experienced master of ceremonies.

"I want you all to become sales managers," he said. "The first thing you've got to do is to get your salesmen excited about the product."

No one among the more than 1,500 people attending the First National Catholic Lay Conference on Evangelization here had to be told what "the product" was, for they had gathered specifically to learn all they could about how to "sell" their church.

A decade ago, an evangelism program in the Roman Catholic Church would never have been considred. But within the last few years, Catholics in this country have been quietly exploring ways both to win converts and to reclaim the loyalties of onetime members of the church who have fallen away.

Clements is one of more than a score of persons around the country who have been involved in such experiments. He and others were invited here for the conference last weekend to share their experiences.

"Evangelization ought to be fun," Clements declard. "If you don't enjoy it, then go serve on the parish council or worry about the budget or take up the collection. But evangelization is fun."

Clements has come to national attention in the church for two programs he has directed as a layman in his suburban Atlanta parish, aimed at unaffiliated Catholics, or what Clements call "Roman Catholics retired."

It is estimated that there are more than 12 million such persons nationwide. They are a prime target for the new evangelization programs. So are the 80 million or 90 million Americans who claim no religious affiliation.

"As a people with a commitment to Jesus Christ and His tasks," explained Msgr. Alvin A. Illig, who directed the evangelization conference last weekend, "we have a duty to Him and an obligation born out of love of our brothers and sisters who know Him to attempt to invite them to share the blessings, hopes, challenges and consolations of Christ that enrich human life."

Illig, a Paulist priest, heads the committee on evangelization for the National Conference of Catholic Bishops.

Unlike some members of the more evangelical Protestant groups, Illig is strongly opposed to any efforts by the Catholic Church to proselytize persons who are already active members of their religious bodies.

"Our basic attitude must be one of friendship," he said. "Our commission as Christians is to invite those in search of a religious family to investigate our family and then create the atmosphere and the opportunities for the enquirer to sample our way of life."

Illig believes that "the hope of evangelizing large numbers of the American unchurched lies with the laity."

For that reason, the conference that he organized here was geared to lay members both in terms of participants and much of the leadership.

Clements offered his own reason why lay members should do most of the work of evangelization. Many "retired" Catholics, he pointed out, have withdrawn from the church because "they have been hurt, often by a priest." Whether the hurt is real or imagined, justified or not, he continued, "that's another reason the lay people have got to do (evangelization))."

"They want to talk; they want to unload on you . . . You've got to tell your people they must listen," he told his newly created "sales managers."

"People out there have never had a chance to unload what's bothering them," Clements continued. "If you're willing to listen, you may be the first Catholic who ever listened" to the reasons for their alienation from the church.

"And even though they are angry, really angry with the church, they will be glad to be invited back," he insisted.

Salesmen of the Catholic faith, Clements admitted have "a very complicated sales pitch. Now the Southern Baptists, where I come from, talk about Christ and the Bible and for them that's where salvation is. Ours is a lot more complicated than than."

At the same time he warned wouldbe Catholic evangelists against delving too deeply into theology. "We're talking to people who haven't given religion a heck of a lot of thought," he said.

For the evangelization of "retired Catholics, Clements recommended leaning heavily on heritage and tradition. "Even though they may not be coming to mass," he said, "they have a great deal of pride in their faith."

To reach these people, Clements offered a "sales slogan -- three little words that say it all . . . three little words that reach back to the memories of sister rapping the knuckles, to altar boys, to novenas, to the first communion dress . . .

"Tell your people," he said to his "sales managers" to reach out and say those three magic words: 'Friend, welcome home.'"