Audiences, as a huckster once observed, are simply crowds of people who are waiting to be organized.

And you can find those crowds anywhere. On college campuses. In nightclubs, both big and gaudy and small and intimate. Broken into tiny groups and sitting in front of televisions. In airports.

That's where Jay Leno finds them. And he charms them, plying them with material designed for the time and place. He's very good at it.

He's especially good at pulling together those little knots of people all over the country who form the television audience. And in his view of the entertainment world there are audiences within audiences, each to be played in different ways. "Colleges are different from nightclubs," he said, "and Carson is different from Letterman."

It was his work on David Letterman's "Late Night" program that formed the germ of his venture into prime time this week. "I found myself talking about my family on Letterman," he said. "I thought it might work on prime time."

The test will come at 10 on Thanksgiving eve when he headlines an NBC special, "Jay Leno's Family Comedy Hour." His guests and coconspirators in a variety of family- and domestic-oriented skits will be a cadre of stars from the network's hit shows: Bea Arthur from "The Golden Girls"; Corbin Bernsen, Richard Dysart and Susan Ruttan from "L.A. Law"; Brian Bonsall from "Family Ties," and Anne Schedeen from "Alf." And there will be the familiar faces of Barbara Billingsley, Florence Henderson, Dick Van Patten, Chao Chi Li, Don DeFore and John Hancock.

The skits, stitched together with stand-up commentary from Leno, will focus on domestic situations -- "how to deal with kids while traveling and so on," said Leno. "We have Brian Bonsall on a plane as a screaming child, pounding Corbin Bernsen on the head.

"We have a then-and-now skit on sex education, then and now. Then, the mother's feeling awkward while reading from a textbook. Now, she's reading from a cable-TV guide."

Leno is in the vanguard of a new run of stand-up comics who are giving that ancient talent a revived place on television. Suddenly a comic form that was dormant for years has come to live with the likes of Arsenio Hall, about to end a highly-praised run as host of the troubled Fox "Late Night" show, and such occasional talk-show guests as Steven Wright, Roseanne Barr and Lou Anderson, who bring fresh material to the comatose artform. Suddenly, television is funny again.

In the case of Leno, in his frequent role as Johnny Carson's fill-in, he combines his own humor with an interviewer's gift, a rare late-night combination.

Leno is low-key and nonchalant in talking about his success on Carson's show, a disposition that is probably the key to that success in the first place.

His success in hosting the Carson show, he said, is partly an extension of his experience killing time in airports. It comes "easily from being on the road a long time," he said. "These are the kinds of airport conversations you usually have -- not like Oprah or Donahue," he said. "It's, 'Hi, how are you? What are you doing these days? Oh! Your plane is taking off ... Now, our next guest is ... "

His approach to the show is simple: "From eleven-thirty to ten-to-twelve I'm a comic. Then I stop and listen to what people say. I'm not trying to be funny all the time. I don't want to get into that lampshade mentality."

Leno's work on television is reinforced by his appearances in clubs and on campuses across the country. He's on the road some 250 nights a year. The gratification of work before live audiences is instant and it serves to keep his TV work in perspective.

Some people perform on television for years and feel they're popular, he observed. The longevity can be deceiving. "Comics can be on television a long time, and then they go into a club and no one is there," he said. "Jim and Tammy Faye were on television for a long time, then they announce a nationwide tour and can't sell 80 tickets."

The live stand-up work offers immediate reward or punishment. "I go to work at eight, by eight-fifteen I know if things are going well or not, and by 10 I've got my paycheck and am on my way home."

Home to Mavis and the motorcycles. Mavis is writer Mavis Nicholson Leno, hs wife. The cycles are what he refers to as his collection of "kinetic art," vintage motorcycles he restores, an extension of his early days as a mechanic.

His early days also included study at Emerson College and work in clubs in the Boston area. When he was 9, his family moved there from New Rochelle, N.Y., where he was born.

He attributes the resurgence of stand-up comedy on television to the economics of small nightclubs, TV's farm clubs, in which he started.

"A lot of it is economic," he said. "You can bring in a single comic for a fraction of the cost of a live band. Comedy clubs are flourishing. A comic can work with a mike and a simple sound system. You can get a known comic for no more than a local band."

And from his standpoint, it's a testing ground for material for television, as well as a source of instant gratification. And if you see Leno in a club, you'll not be hit with X-rated humor.

While many comics are flocking to cable, the relatively uncensored side of television, Leno doesn't mind the boundaries of prime time. Working clean "is a marketing decision, not a moral one," he said. "I find I get more laughs working clean. Working clean I get more publicity and larger audiences."

Political humor, he said, is also closer to the cutting edge. "I find it more interesting to get my message across ... to an audience that's not primed for a particular type of humor," he said, referring to comics who work blue and their audiences who expect it. "Obscenity and sex jokes -- there's nothing daring about them. I always considered Mort Sahl to be more daring than Lenny Bruce."

The clubs can serve as a barometer telling Leno whether a particular joke is too close to the cutting edge for broadcast TV. While the country was breathing easier over the rescue of little Jessica from the well in Texas, Leno was coming up with some lines he wanted to spring in a club before delivering them on the Carson show.

"She was doing fine, but what an ordeal," he said, "in the well for 58 hours and then having to meet George Bush. It's enough to make her want to go back down."

And then, he recalled, Bush talked about how the concern for Jessica demonstrated how Americans band together to help a child in distress. "Come on," said Leno. "As if the Swiss would have let her die! As if anyone else but Americans would have sealed the hole and buried her!"

He likes to think that in the long run his barbs are distributed all along the political spectrum. He recalled a Wall Street Journal story mentioning that he was one of the few comics to have done a pro-Bork joke when that Supreme Court nomination was up in the air. "The joke was that Ted Kennedy had accused Bork of opposing simple justice," said Leno. "That from Kennedy who was avoiding simple justice.

"But I had also done an anti-Bork joke, talking about the governor of Arizona, who may be forced to step down. That would be good, I said, because Reagan may need someone to replace Bork."

Leno prizes the opportunities he gets to deliver the opening monologue while pinch-hitting for Carson, and his appreciation of Carson himself is obvious. "If the stock market crashes," he said, "I want to hear Johnny's monologue. I hosted the night the Iranians blew up a Kuwaiti tanker with a Chinese silkworm missile. I said Reagan was mifffed because the missiles we sent weren't good enough."

The key to successful comedy on television is simple, he said. "It's just the joke," he said. "The mistake a lot of comics make is trying to get their own opinion in two feet ahead of the joke. I don't think anyone knows whether Johnny Carson is a Republican or a Democrat."