Ask actors about the craftwork involved in developing their character and they will quite often speak of a moment — a costume fitting, a line read, a voice and diction session — when they felt that figure take over and they became engrossed in the role.

For “Lady Bird” star Laurie Metcalf, nominated this year for a supporting actress Academy Award, it began with a hairclip.

“When I got the hair going and was able to throw it up in the back with a clip and that really looked [like] somebody who had other things on her mind than what she looked like for the day,” Metcalf says of her role as Marion McPherson, the harried matriarch who is frequently set as an unwitting sparring partner against her teenage daughter in writer-director Greta Gerwig’s much-praised production about a struggling Sacramento family in the early aughts. “She’s a nurse and was pulling long hours at the hospital. But also, it was the mumus and caftans that I got to wear. I thought this is so period and
I can hook into this. That was really helpful.”

She adds that she felt it again when she they almost wrapped the movie — when she was, ironically, filming what would be one of its opening scenes. It involves an impromptu argument between her character and Saoirse Ronan’s titular (anti)heroine during a mother-daughter bonding exercise in the form of a long car ride; an event Metcalf says “set this unexpected tone through the whole movie.”

“That scene really clicked with me [and] made so much sense,” Metcalf says. “Saoirse and I and Greta had a really strong relationship by then. We were so comfortable by then. I just had such a really great time getting that opening scene up to speed and working with the overlap [dialogue] and making it kind of messy and making it really spontaneous. We got to do that scene, I don’t know five or six times in the car.”

It probably helped that Metcalf has four children of her own and, of course, was once a teenage girl herself. But sometimes actors relate to their parts because they draw from further back in their genealogy. Mary J. Blige, who is also nominated in the supporting actress Oscar category, says it took “a couple of days for me to actually even surrender to the stripping down” that director Dee Rees required to turn her, a glamorous and well-coiffed musician and record producer, into Florence Jackson, a World War II-era Mississippi sharecropper.

“It was like the second day that we started shooting. As soon as we hit the set, she just took over,” Blige says of her character in the film, which Rees co-wrote with Virgil Williams. “Once the hair was done like Florence’s hair and once I put on the dress that was sent over for Florence and the slip that went under the dress and the little black boots that went with it. … Once the cameras were on, Florence was born. She was in play.”

This also might be because once she gave in, she didn’t just see a role when she looked in the mirror: She saw her own grandmother Catherine Miller starring back at her.

Blige says that she even caught a moment in the film where she says, “I’m standing with my hand on my hip and my legs go back like my grandmother’s legs. It was like my grandmother and my ancestors were just taking over at that moment.”

Not all actors have this epiphany as immediately or suddenly. “Phantom Thread” supporting actress nominee Lesley Manville says the film’s writer-director Paul Thomas Anderson graciously gave her the script about seven months before he began shooting. In addition to her own research into the period, she got to have “many, many costume fittings” with designer Mark Bridges. These helped her establish that her character of Cyril, an omnipresent and supervising factor in the life of lead Daniel Day-Lewis’ fashion designer, Reynolds Woodcock, “was going to be a very neat, a very well-tailored, scary and precise-looking woman.” She also appreciated that Anderson did not rush through scenes; rather he allowed her and the other actors to experiment with various reactions.

“Paul Thomas Anderson; he’s not very prescriptive,” Manville says. “He doesn’t say she needs to be this, she needs to be that. He lets you do your thing, which is glorious. When I started doing her on set, that’s when he really starts to get fired up. I would start to do Cyril in this very scary way. You can do a lot with a look and a glance. He loved it. And, so, he would encourage me to push that a bit further. And then have a delivery with my lines that’s quite clean.”

Because she was allowed to fully immerse herself in the experience, Manville was able to establish in every scene that “there’s always something quite pristine about the way she does everything; about the way she walks, how she talks, the way she does her hair, the way she dresses.”

And while lead actor Oscar nominee Timothée Chalamet may not have gotten as much time as Manville had to prepare for his breakout turn in director Luca Guadagnino’s coming-of-age period drama, “Call Me by Your Name,” he appreciates that they had, what he calls, “the gift of being able to shoot chronologically during production.”

This was on top of the month and a half of preparation he had after he arrived on location in Crema, Italy, to absorb the scenery and develop his interpretation of teenage Elio by taking piano and guitar lessons, learning Italian and (perhaps most importantly) eventually striking up a bond with Armie Hammer, who plays his love interest in James Ivory’s adaptation of the beloved André Aciman novel.

“The pre-production process was crucial to this film, it was a great fortune to get to know everyone quite personally before starting,” Chalamet says. “I felt myself becoming one with the story and the role after shooting the very first scene, where Elio is preparing his bedroom for the anonymous American’s arrival” that would be Hammer’s Oliver.

“Paul Thomas Anderson; he’s not very prescriptive. He lets you do your thing, which is glorious.”

“The first couple of set-ups went so smoothly, and it felt like we were providing Luca what he needed,” Chalamet says. “And there was a feeling of joy and camaraderie in beginning the film. In large part it felt like that for the rest of the shoot.”

“Phantom Thread’s” Manville knows all too well that this sedate strategy is not common. A television and theater veteran who is starring opposite Jeremy Irons in “Long Day’s Journey Into Night” in London’s West End, she says, “I equally like that challenge” of diving head-first into something and trusting your gut.

“You have to adapt, as an actor, to the different circumstances that you find yourself in,” she says. “If you shoot a TV series where there’s much less time to shoot and usually no rehearsal time, that’s very much to do with your gut instinct and you have to work in a more immediate way and you have to really come to the table prepared and you have to know what you can do.”

But, of course, there are some instances where duty calls and you have almost no prep time at all. Christopher Plummer famously replaced Kevin Spacey as J. Paul Getty in director Ridley Scott’s “All the Money in the World” just three days after reading the script (and was rewarded for it with a supporting actor Oscar nomination). He says the lack of time for second-guessing actually helped in this case because the oil tycoon had “so little of a personal nature about him.”

Luckily for Plummer, he was able to rely heavily on screenwriter David Scarpa’s “take on him, which he did wonderfully; giving me an array of different colors to work on.”

This isn’t necessarily the venerable actor’s normal process, however. Rather, Plummer says, “it depends on the familiarity or the complexities of each famous character.”

For example, Plummer says he “had no need of research for Mike Wallace,” in director Michael Mann’s “The Insider.”

“I’d watched the man all my life on TV. But the kaiser, in ‘The Exception,’ I needed a lot of research, as I did with the Duke of Wellington in ‘Waterloo.’ But, mostly, I rely on my instincts.” Plummer says he felt he most understood Getty in a pivotal scene in which “he confesses that he prefers ‘things’ [like] works of art, architecture, paintings to people because they never deviate or change but remain the same and never let him down.”

Plummer adds that whenever he could, he looked “to find a grain of humanity in the man.”

Well, not all characters are so easily relatable.