Great casting is like finding a great relationship: it involves a rare synergy that often can't be described in words. Sometimes, you get it on the first try; other times, it takes 15,000 rejections to find the right one.

At the Tribeca Film Festival, esteemed casting directors Ellen Chenoweth and Ellen Lewis sat down with their mutual friend, theater and casting director Bernard Telsey, in a rare discussion of their casting careers. Between them, the Ellens have cast dozens of Best Picture nominees and winners, from Goodfellas to Forrest Gump to Gangs of New York to The Aviator.

"You don’t want to fully expose the rejection that people went through," Lewis said. "It’s private. That has [created] a shroud of mystery about what it is we do."

In fact, The Academy only just created a separate branch for casting two years ago. Here's what we learned from the accomplished women as attempted to lift the veil of mystery from the intricate—and oftentimes exhausting—process of casting.

"To be an actor, your goal in life is to go to as many job interviews as you can on a given day. My goal in life is to go on as few!"

1. Don't get locked into pre-conceived notions 

True_grit_-_hailee_steinfeld_-Hailee Steinfeld in "True Grit"

Lewis and Chenoweth emphasized the importance of open-mindedness when casting. The script should never have the final word—even if a role is written a certain way, both directors and casting directors should be open to other possibilities.

When casting Wolf of Wall Street forMartin Scorsese, Lewis was having trouble finding the right person to play Donnie Azoff. "We ended up casting Jonah Hill, but that part was not written funny," Lewis recalled. "It was Marty’s idea to do improvs with people and go off-book. It made it all come alive. Marty loves dangerous comedians. We laugh a huge amount in casting sessions, amidst murder and mayhem."

Chenoweth experienced a similar breakthrough when casting True Grit for the Coen Brothers. "We were looking for a scrappy little Holly Hunter from Days of Heaven Southern girl, and we ended up with a beautiful girl from LA who was poised and formal," she said. "You can’t be too locked into what you think you’re going to need."

"I love small parts. I want to be in the sessions; I want to hear the one word they have to say and see if I believe it."

2. It's true: "There is no small part"

It's a truism that often seems directed at bit-part actors to boost self-esteem, but Chenoweth and Lewis confirmed the fact that casting directors take small parts very seriously.

"I love day players," said Lewis. "I see a movie as a big painting with faces. As opposed to a play, where actors really need great skill, in movies, if somebody looks right and feels truthful and can deliver the line or the word, you can go with them."

For Lewis, small parts are essential to building out the film's world. But while a small part can be an up-and-coming actor's big break, sometimes Lewis prefers the real deal. "I’ve cast movies like Casino where I was in Las Vegas for about 3 months and all these real people were coming in, and it ended up that I cast a lot of real people," she said. "I love small parts. I want to be in the sessions; I want to hear the one word they have to say and see if I believe it. Because that’s what casting’s about—Do I believe what you’re saying? Does it seem truthful? Does it fit the world that the character lives in?" 

"Ideas are everywhere. That’s the great thing about casting in New York. When you’re in LA, everyone looks like you."

3. Street casting is legitimate

Lewis, whose mentor was the legendary casting director Juliette Taylor, was trained to favor street casting. "We would go to Little Italy, Jewish old age homes, schools in Brooklyn looking for young Woody Allens and other odd-looking children," she said. "Ideas are everywhere. That’s the great thing about casting in New York. When you’re in LA, everyone looks like you. In New York, all you have to do is walk out the door and you see the world. I find it so stimulating. It feeds your imagination."

4. ...But sometimes, you cast a murderer by accident

When casting Goodfellas, Lewis experienced the bizarre dark side of street casting. "A very decorated cop came in with another actor to meet Marty," she remembers, "and he looked really interesting and had all these pictures of bodies, and we put him in the movie. Eight years later, I’m watching the news and they’re talking about these two highly-decorated New York cops who have been arrested for murder." As fate would have it, Lewis and Scorsese had cast a real hit guy for the mob. (He's currently serving a life sentence in prison.)

5. Casting children is like finding a needle in a haystack

Shot03"Forrest Gump," cast by Ellen Lewis

Casting children is notoriously difficult; sometimes an entire production hinges on the ability to cast the right child actor. "It's hard when the whole movie depends on one thing," said Chenoweth. When casting True Grit, she had to find the perfect 12-year-old girl. "It’s a lot of pressure. I think we saw 15,000 girls. It got a little late in the game when we found Hailee [Steinfeld]."

"On Forrest Gump, which was one of the first things I was casting on my own, finding Young Forrest was incredibly challenging," Lewis recalls. "There were open calls going on and nothing was working out. They were almost going to have to push the movie because we could not find that boy. It was so stressful. I remember calling Juliette from some hotel and crying." Finally, after conducting an open call in Mississippi, Lewis found the right little boy. "Tom Hanks actually stole the boy’s accent," she said. "That is how that boy spoke. It wasn’t the other way around."

Finding just the right adult for a role can be just as challenging. Chenoweth remembered getting down to the wire before she found Josh Brolin for No Country for Old Men.  "Somehow it was hard to find a guy who was a manly, screwed-up Vietnam vet and a little bit of a loser," she said. "But he was just it at the right time."

6. Casting directors try to be kind to actors

Lewis's biggest takeaway from her eight-and-a-half years studying under Juliette Taylor was the importance of being kind to actors. "I mean, come on!" Lewis said. "To be an actor, your goal in life is to go to as many job interviews as you can on a given day. My goal in life is to go on as few! They’re facing constant rejection. It’s our job to make that experience comfortable and warm. We want them to do well. We are looking to cast something, but ultimately one person’s going to get that part. You just hope that at least the experience of coming into our office is positive because that’s the only thing we have control over."

Be sure to check back for more coverage of Tribeca 2016.