Writer/director Todd Berger had a lot to worry about during the slam-bang 14-day shoot for his second film, “It’s a Disaster,” the story of four couples gathered for Sunday brunch who discover the world might be coming to an end.

But what concerned him most was simply making sure the actors were looking in the right direction when they spoke to each other.

Writer/director Todd Berger had a lot to worry about during the slam-bang 14-day shoot for his second film, “It’s a Disaster,” the story of four couples gathered for Sunday brunch who discover the world might be coming to an end.

“The hardest thing for me to do is keep track of eyelines,” Berger confesses.

Script supervisor Shannon Volkenant came to the rescue, devising a series of color-coded overhead diagrams indicating where the actors were standing and which direction they were looking, ensuring the camera coverage made sense at all times.

“The final dinner sequence had six hours of footage for 10 minutes of screen time,” Berger says. During editing, “the fact everyone was looking in the right place all the time was a godsend. I told Shannon at the premiere, ‘You are the glue who held this movie together.’ ”

While the above-the-line talents (writers, directors, actors and producers) steer a film creatively — and receive the lion’s share of the money and the glory — they often find themselves turning to their below-the-line coworkers (d.p.’s, production and costume designers, editors, vfx artists) for tips, tricks and hard-learned lessons.

The collaboration often starts during pre-production.

Faced with exponentially more action in “The Bourne Legacy” than his previous directorial efforts, Tony Gilroy (“Duplicity,” “Michael Clayton”) began consulting with stunt coordinator Dan Bradley more than nine months before the start of principal photography. “I brought in Dan even before the script was finished,” Gilroy says.

On “The Watch,” starring Ben Stiller, Vince Vaughan and Jonah Hill, writer-director Akiva Schaffer learned from storyboard artists Chris Hunter, Trevor Goring and Joel Venti how freeing it was to work out all the shots visually before cameras rolled.

“It was like studying,” says Schaffer, a longtime “SNL” scribe who previously helmed 2007’s “Hot Rod.” “By the time it was test day, I knew everything. It gave me the confidence to make changes on the fly, because I knew the material so well.”

Sometimes the crafts people might offer a simple nudge, as when the hair and makeup artists on next year’s “Kill Your Darlings,” set in 1944, told actor David Cross that the beard he favored would not be era-appropriate for his role as the father of poet Allen Ginsberg, played by Daniel Radcliffe.

“We discussed it and decided they just didn’t wear them back then,” says Cross. “What’s factually correct wins out.”

But period correctness doesn’t always triumph. On the upcoming “The Perks of Being a Wallflower,” set in the early 1990s, writer-director Stephen Chbosky resisted costume designer David C. Robinson’s suggestion that the characters wear period-correct but tacky acid-wash jeans

“I said, ‘OK, give them to the extras,’ ” Chbosky recalls. “It can be there, because it’s real to the period, but I wanted our core kids to be relatable fashion-wise to contemporary audiences.”

In the cast of “The Expendables 2,” production designer Paul Cross’ contributions actually altered the storyline.

Shooting the film at the aging New Boyana Film Studios in Bulgaria last year, director Simon West had to contend with an ever-expanding line-up of action film legends from Sylvester Stallone to late addition Chuck Norris, all with varying schedules.

So West and Cross centralized the shoot on the studio’s backlot and rewrote the script accordingly.

A half-built New York street became an Eastern European camp to train moles for spy missions, Cross altered a Middle Eastern set to look like a street in Southeast Asia and West rewrote the opening sequence for the setting.

“We walked past this rundown ’60s building where the production accountants were and (Cross) said, ‘I could cover it with some fading paint and it could be a great outskirts of town for the opening sequence, as well,’ ” West recalls. “There wasn’t a building on the backlot he didn’t adapt or paint or alter in some way so I could get this huge look that will make people think we either went to all those places or built these giant sets.”

Todd Lincoln, writer-director of upcoming horror film “The Apparation,” believes above-the-line talent should pay close attention to everyone on the set.

“I love the idea of the crew as a small family or team and just being open to different ideas,” Lincoln says. “It can be from a P.A., the craft service guy or an electrician. I’ll take a good idea from anywhere and incorporate it if it’s right.”