LOS ANGELES, Calif. - Alexander Payne, director of "The Descendants," likens it to "inviting people to my home for dinner."

"Bridesmaids" director Paul Feig describes it as spending hundreds of hours waiting for that "one aha! moment."

Tate Taylor, who wrote and directed "The Help," uses starker terms when describing the process of crafting the perfect acting ensemble: "One bad casting choice, one weak link, can spell death for your movie. That's why you see tons of people and you don't stop until it's right."

"The Help," ''The Descendants" and "Bridesmaids," along with the silent movie "The Artist" and Woody Allen's "Midnight In Paris," are vying for the Screen Actors Guild's ensemble trophy at Sunday night's 18th annual SAG Awards.

SAG began giving its movie ensemble award in 1994, after an equivalent trophy for favourite television cast proved popular in its inaugural awards show a year earlier. The honour, says SAG Awards producer Kathy Connell, originated with the guild and reflects its desire to "acknowledge the creativity of chemistry and the teamwork that actors do."

Which is fine by the directors of this year's nominees, many of whom spent more time casting their movies than making or editing them.

Payne began casting "The Descendants" nine months before filming began, starting with George Clooney, whom he had politely rejected for the lead role in his last movie, "Sideways." Payne takes a unique approach to building an ensemble, working with a single casting director, longtime associate John Jackson, for hiring the lead roles, the locals and the extras.

"I don't like the Hollywood system of hiring three different people for casting," Payne says. "I don't want to explain myself three times over. I think one person should be in charge of all the flesh in front of the camera and bring a single vision to that."

Critics frequently praise Payne's knack for placing actors in unlikely roles. (Think Kathy Bates' twice-divorced mother who enjoys a "white hot" sex life in "About Schmidt.") He and Jackson did that several times over in "The Descendants," starting with casting Clooney as a clueless father who wears, as the actor puts it, "khakis up to his armpits."

"If I cast against type, I do so unwittingly," Payne admits, "because in reality I don't see that many contemporary American films. So I don't know the actor's type to begin with."

That was not the case for Taylor, who, when adapting longtime friend Kathryn Stockett's bestseller, wrote the roles of Minny and Charlotte specifically for two other dear friends — Octavia Spencer and Allison Janney, respectively. In fact, Taylor and Spencer were roommates in Los Angeles when Taylor wrote the screenplay.

Taylor also wanted Viola Davis for the lead role of maid Aibileen, and pushed the film's start date to accommodate her schedule. Determined not to "cast from the covers of magazines," Taylor threw the doors open for the rest of the movie's large ensemble, hiring, among others, Emma Stone and Jessica Chastain before they became in-demand actresses.

Three weeks before filming, Taylor brought the cast to Mississippi, rehearsing in the locations where they eventually filmed.

"Mississippi infiltrated the cast and a family dynamic formed," Taylor says.

Rehearsals were critical for the "Bridesmaids" ensemble as well, Feig says. The cast met two months prior to filming, reading through the script and then going through rigorous improv sessions so Feig and the movie's writers could tailor new material to the actresses' strengths and personalities.

During this revision process, the filmmakers expanded Melissa McCarthy's part, most notably, putting her in a key, emotionally layered scene opposite Kristen Wiig late in the movie. McCarthy wound up being the one individual "Bridesmaids" cast member nominated for a SAG Award.

"It's when you're rehearsing more and more, you start to think, 'Wow. These girls together are strong," Feig says. "That's also when, as a director, you get nervous. You're thinking, 'Oh boy. I'm the only thing that could throw this all off.' "

Since Screen Actors Guild began giving its ensemble awards, other groups, like the Broadcast Film Critics Association, have jumped on the bandwagon. Television's Emmy Awards added three casting categories in 2000 and some in the industry, like "Modern Family" co-creator Steve Levitan, believe an acting ensemble award should be added, too.

Meanwhile, the Academy of Motion Picture Arts and Sciences, which added an animated film category in 2001, has no plans to supplement its four acting honours.

As it stands, members of popular ensembles, like Chastain and Spencer in "The Help," often find themselves in competition for a film's top accolade.

"If the actors give distinctly different performances, they stand on their own and don't cancel each other out," says Kristopher Tapley, executive editor of awards coverage website In Contention.

The beauty of SAG's ensemble award, says Taylor, is that, for one night at least, "everyone's on the same team."

"It's going to be a great reunion," Taylor adds. "It might get a little loud, though."