It’s one of the most dramatic changes in career-course direction in Hollywood — from spending months fine-tuning a prospective pilot script to helping guide a team of writers, actors and crew members to bang out three episodes of your first TV series every month.

Liz Meriwether, creator of Fox’s “New Girl,” which both made Zooey Deschanel a household name and helped reverse the network’s live-action comedy fortunes, can attest to how her hit series changed her life.

“I used the sleeping bag in my office a lot,” says Meriwether. “I learned about the dry shampoo — you spray it on your hair and it looks like you’ve washed your hair. I can tell you where all the showers are on the Fox lot.

“If someone had told me in advance what it would be like, I may not have signed up,” she adds, again joking. “But I’m glad I did. All of it was pretty fun. It’s also the hardest job I ever had.”

Meriwether’s first challenge came early on, when pilot co-star Damon Wayans Jr. was wrested from the cast when ABC unexpectedly renewed “Happy Endings,” necessitating the hasty creation of a character.

“We broke the first seven episodes’ (storylines) without having cast Winston (Lamorne Morris eventually won the role). We didn’t know what stories to break because we didn’t know his character. It took the back half of the season to figure it out.”

The chief lesson Meriwether learned in her first season of “New Girl” was to trust collaborators.

“One of my biggest personal struggles was, when I was stressed out, I’d retreat within myself into my office,” she recalls. “I was always rescued by remembering I was surrounded by such talented people. You need to have a vision for your show that you communicate to people but be open enough to allow other people’s visions to be incorporated.”

By contrast, Jonathan Nolan, exec producer of CBS’ “Person of Interest,” was looking forward to collaborating in a writers room, having spent much of his career “getting caught by security guards on the lot talking with the voices in my head on the snow-covered ‘Gilmore Girls’ set. The opportunity to make it a real conversation with other writers excited me.”

Until, that is, he actually spent time in the writers room and had to discourse with voices other than those in his own head.

His collaborator, showrunner Greg Plageman, adds with a laugh, “He’d turn to me and say, ‘When does it stop?’ ” Plageman also recalls Nolan, due to his features background, being unduly deferential to the show’s visiting directors, not realizing that in television writers actually have more power.

“I approached the job with a kind of healthy amount of ‘I’m an idiot who doesn’t know what he’s doing,’ and it’s kind of worked,” he says. “The show is everything I hoped it would be and everything I feared it would be, at once.”

As a former writing supervisor on “Saturday Night Live,” Emily Spivey was ready for the grind of weekly TV production. But on “Up All Night,” she still encountered plenty of challenges to surmount.

“I liken it to childbirth in a way. No one can really prepare you for what it’s like to have a baby or to have your own show,” Spivey says. “I thought, coming off ‘SNL,’ it would be easy to deal with so many personalities. But writing’s just a small part of it. You have to manage such a large staff.”

The show’s pilot was significantly retooled, turning Spivey’s ‘SNL’ collaborator Maya Rudolph’s character, Ava, from a publicist into a neurotic, Oprah-esque talkshow host.

Spivey recalls the best advice she received.

“Don’t try to do everything yourself and don’t feel guilty if you’re not in 25,000 places at once,” she says. “I was initially trying to run myself ragged when my emphasis was supposed to be on coming up with good scripts.”