Tools of Characterization
Characterization in Vertigo
Clothing
The iconic costume designer and Edna Mode lookalike (seven Academy Awards, countless nominations) teamed up with Hitch for several of his biggest ventures. Ms. Head's work for Vertigo goes a long way toward making Madeleine who she is—and making Judy who Madeleine's not.
Clothing plays a key role in communicating both Madeleine's elegance and her otherworldliness, as her gowns stand out among the merely human diners at Ernie's Restaurant, and as she runs errands in her signature grey suit. Hitchcock requested a gray suit because he knew that gray tends to wash out fair complexions, and he wanted to give Madeleine a ghostly appearance. Her wardrobe masks her sexuality—nothing too revealing. (Source)
Judy, on the other hand, is a salesgirl in casual clothes and a girlish hairstyle when Scottie meets her. She's a little rough around the edges, and she's wearing a ton of makeup compared to Madeleine. Her clothes are more colorful. She has a lot of cheap scarves and belts and costume jewelry, all which make her look much less classy. Also, she's more overtly sexy than Madeleine, with that tight sweater (and no bra, remember?). The fact that we can see her body communicates to the viewer that she's a real person, as opposed to Madeleine, who's a ghostly fantasy.
Scottie's obsession with Madeleine's clothes—as shown when he forces Judy to buy a whole new wardrobe—underscore their importance. The characters of Madeleine and Judy gradually converge as Judy dresses more like Madeleine and dyes her hair, and as Scottie's reality becomes blurred. Once Judy appears in Madeleine's gray suit and blonde up-do, she's become Madeleine in Scottie's eyes. They're no longer different women for him.
Novak loved wearing Judy's comfortable, soft clothing; she could physically relax, and you can see that in Judy's character (source). She hated the clothes Hitchcock made her wear as Madeleine, especially the stiff and uncomfortable gray suit. She couldn't wait to get out of it at the end of the scenes. However, she said she found a way to use that discomfort to play the character, a woman forced to be aloof, someone she wasn't, desperate to break out and reveal her true self. (Source)
Actions
As for Scottie, his actions speak for themselves and reveal more about him than anything he wears—or anything he says, for that matter. It matters that we first see the film's protagonist when he's in the middle of a rooftop chase and has a failure of nerve. This sets us up for a basic action premise of the film: his fear of heights and the vertigo it causes. He's an active, risk-taking detective who becomes paralyzed by fear.
At first he's a passive watcher of Madeleine, but after he saves her from her jump into the bay, he becomes more actively involved with her. After her "death," his passivity becomes catatonia, sitting in a mental hospital not moving or speaking.
Once he meets Judy, he becomes more and more active and dominating. Near the very end of the film he becomes shockingly aggressive, taking Judy against her will back to San Juan Bautista and literally forcing her up the stairs of the bell tower. He's trying to cure his acrophobia and regain some sense of masculine power. With Judy's death, however, he returns to a passive, stunned state. As Scottie's demeanor changes during the course of the film, we get a close look into his psychological conflicts and how they're manifested.
Dialogue
Hitchcock, master of visual storytelling, liked to say that a director should only resort to dialogue as a last resort, when just the image couldn't tell the story (source). The dialogue of the characters in Vertigo supports their characterization, but isn't the most important thing about them.
Midge is perky and practical; she speaks in a teasing but straightforward way, good with a snappy comeback or no-nonsense comment. Scottie has an easygoing if weary way of speaking, measured and rational until he meets Madeleine. After that, his dialogue becomes very melodramatic. Madeleine, as the troubled soul she is, speaks in vague, mysterious ways; at times, she speaks as if she's directly channeling Carlotta. She says things that don't make sense; she gives out some information then withdraws.
Judy's dialogue paints her at first like the working girl she is—plain language, not especially sophisticated. She's more chatty and plain-spoken than Madeleine. When she starts looking like Madeleine, she begins to sound more like her, almost like she's under a spell, but this time it's under Scottie's spell.