MIAMI BEACH — She was amazingly beautiful in her white halter top and miniskirt, surpassing even the Himalayan standards of South Beach. As she danced on a velvet ottoman here at a club called Mansion, she turned more than a few heads, her curly black hair swaying back and forth as the music pulsated and the strobe lights darted across the dance floor.

Who was she?

"I'm a party girl, baby!" is all she'd say.

Was she a plant of the human variety? Was she paid to be there? Not even the promoters of the evening could say for sure.

But it's rarely by chance that such beauties find themselves at A-list parties these days, parties like this one, where Paris Hilton and her entourage were reigning from the roped-off VIP area on Mansion's main stage.

Like the Wilhelmina models decorating a party over at club Privé, they're here because of what they can bring to the scene: glitz, glamour and buzz.

In party towns such as Las Vegas and Los Angeles, New York and Miami, they're called "party motivators," pretty people who add a certain energy to an event. Art galleries even use them to spice up openings and help sell the merchandise, dubbing them "gallerinas."

But Ingrid Casares, a leading party promoter here and gal pal of Madonna's, prefers another term: "I call them eye candy. We've been inviting eye candy since the beginning of nightclub life down here."

Sometimes just being pretty is enough to get you in the door. And sometimes you're paid hundreds to share your smile.

"People always say to me, 'You have a lot of models at your parties!' " says Lana Bernstein of trendy Ocean Drive magazine. "But it's just as important these days as the decor and good lighting."

Maybe more.

Casares has it down to a science.

"You motivate them to come in by giving them a table and letting them drink for free. If they were savvy enough, they'd ask for money, but here they're willing to drink for free, so that's good for us.

"You figure out who's (hanging out) with the good-looking models, who has a posse they bring with them," she says. "You want them to make the party happen. Then you focus on those people, make friends with them, make a deal with them — bring in 13 models, say." Casares says she'll either pay someone $150, or if not, "we'll give them a couple of bottles."

It's a win-win deal for everyone.

"It works for the (modeling) agency, works out for us, too. We mostly want girls, because that brings in the men who spend money on the bottles. You want them to come in and dance on the bars."

Who gets hired and why There are three primary characteristics that make for a successful party motivator, says Michael Cerbelli, creative director at Total Entertainment in Englewood, N.J.: looks, personality and talent. While many party motivators boast some degree of all three, most tend to fall into a "type": Eye Candy. "You could say these young men and women are so beautiful that guests will do anything just to be near them," he says. Think Halle Berry. Good Timers. "Able to relate to anyone, from a 13-year-old boy to a 60-year-old woman, Good Timers use conversation as a tool to relax and involve guests," Cerbelli says. Think Tom Hanks. The Entertainer. Whether it's dancing, singing, magic or juggling, Entertainers draw the guests into the festivities by getting them actively involved. Think Justin Timberlake.

Or push a product your client is promoting. At a party at South Beach's National Hotel during the MTV Video Music Awards weekend, a bevy of beautiful young women circulated among the poolside crowd, handing out chilled Miller Lite. Clad in matching stiletto heels, white halter tops and miniskirts — practically a uniform on the club scene here — they looked like a cross between NFL cheerleaders and Romans who had large portions of their togas ripped away.

Only smilers need apply

"It's a night of fun, of networking," says Joannah Henley, who is just beginning her career as a party motivator and promotional model in Miami. "It's a chance to be exposed." She was paid $200 for the night, which began at 11 and ended around 4 in the morning.

Isabella Jade is a two-year veteran of the trade, having just moved to Miami from New York. "You have to have a great smile and a good personality, and you have to be able to mix. And you have to be able to wear these heels and not complain," she says. "It can all lead to other things, other jobs." (American Idol runner-up Justin Guarini, for instance, got his start as a party motivator.)

Sometimes a great smile is all you need.

It worked for Blanca Dicos, a nutritionist who drove from Naples to see if she could get into the Paris Hilton party at the Mansion. "I just smiled, and we got right in," she says.

No small achievement, as hundreds were pushing and shoving their way toward the doorman to get his attention and eventual nod to enter.

Dicos, an attractive blonde, was wearing a black sequined top and tight jeans, which probably didn't hurt her chances any.

"In the '80s, it was about celebutantes like Dianne Brill, who were one in a few ruling the club scene," says Tom Julian, a trend analyst for advertising giant Fallon Worldwide who was in Miami observing the MTV festivities. "Today it's a cast of eclectic characters ... unique identities, style statements and distinct stories. Everyone on the scene has a visual vibe."

Translated, that means you're either pretty or have a quirky style that will help the host get his party off the ground. Julian, for instance, says he spotted at least three Lenny Kravitz look-alikes at parties over the MTV weekend.

And more than a few Britney Spears wannabes wandered the recent Blender magazine party at The Shore Club, adding a bit of a Fellini-esque atmosphere to the festivities.

"But no one has been paid to be here tonight," confessed promoter Noah Tepperberg, who was happy to have "real" celebrities there in the likes of Jessica and Ashlee Simpson and Mary-Kate and Ashley Olsen.

Going for the right mix

One of the pitfalls of this "motivator" phenomenon is never knowing who really belongs and who is just there as scenery.

Were the pretty women lounging on the divans and pillows in The Shore Club's outdoor courtyard just more pretty faces, props for the evening?

Both actress Noureen Dewulf, who is filming National Lampoon's Pledge This! with Paris Hilton, and Kiely Williams of the R&B group 3LW said they were there legitimately — although Williams, looking around at the human scenery, confessed "this party has a nice vibe to it."

Tepperberg, a prominent party promoter in New York, learned long ago how important it is to gather together the right people. "We work with talent managers, publicists working with celebrities and assorted 'interesting' groups of people," he says. "And depending on the event, we go out and produce an audience."

He calls it "audience production."

"Each event has a formula, and it's always important to make the right mix. Sometimes it's models, athletes, entertainers, A-list celebrities. It all depends on what the people are looking for.

"People hope to go to events to meet people and network," he says. "But just being good-looking and 25 doesn't necessarily get you on the guest list. ... If you're a movie producer or actor, chances are good you'll get invited."

Nothing is left to chance. Tepperberg's VIP room at The Shore Club had a long table where the Simpson sisters sat back to the wall, facing out to the throng passing by. To see and be seen.

"It's how you seat the room that's important," he says.

All this manipulation isn't just in the adult world, either.

Party motivators also are showing up at bar mitzvahs from

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