Grand Staircase Entrance

Music up as every eye goes to the head of the stairs, the portières move and Mrs. Levi steps through, handsomely gowned, red hair done up magnificently on top of her head. She descends stairs as Waiters, etc. await her first words.

—Hello, Dolly!, stage direction preceding title song

Maybe she's the Girl Next Door who's just gotten a makeover, and it's time to show her family. Maybe she's the Cinderella Expy making her grand entrance at the ball. Maybe she's just finally ready for her date. So how does she ensure her entrance 'wows' everyone there?

She'll appear at the top of a wide, sweeping staircase. (Bonus points for marble banisters, fancy new carpeting, or spotlights.) She pauses a moment, either at the top or a few steps down, so everyone has a chance to take in her beauty, how nice her face is, and her elegant hair and clothes (would even involve a Pimped-Out Dress in older stories). Once noticed, she slowly and gracefully descends.

This is perhaps the only way to justify the camera starting at the feet and slowly panning up the figure. When wearing a dress with a long skirt, stepping down gives her a chance to show off her shoes and legs without being immodest.

Often, but not necessarily, combined with She Cleans Up Nicely.

Examples of Grand Staircase Entrance include:

Film - Live-Action

Hermione's arrival at the Yule Ball in the fourth Harry Potter movie.
Gone with the Wind did this with Scarlett.
Galadriel in the first The Lord of the Rings film.
A tragic version in Sunset Boulevard, as she's breathtakingly attractive only in her own mind--"I'm ready for my closeup, Mister Director."
- It's also a subversion - it's a Grand Staircase Exit.
Igor—Eva makes her entrance just before the Evil Science Fair, complete with Shout-Out to the Sunset Boulevard scene.
Eliza's official debut at the big fancy ball in My Fair Lady.
Subverted in Ever After—she makes her entrance all right, but It Gets Worse.
- Although, notably, she enters up the stairs, not down.
Lainey Boggs shows off her new look after her makeover in She's All That, although this is done on the stairs in her suburban home.
Daphne makes several of these in What a Girl Wants. They proceed from funny, to serious, to heartbreaking as her spirit is slowly broken down and she conforms to upper class British society.
Jerry Lewis in Cinderfella shows up at the grand ball in a big entrance on a huge staircase.
Loki in The Avengers shows up at a museum gala in Stuttgart, Germany, strolling down a huge marble suitcase in an impeccable suit to the soothing strains of a string quartet.
In Disney's live action Cinderella from 2016, Cinderella accomplishes this quite by accident, arriving at the ball a bit past fashionably late, just as the first dance -- for which the Prince will choose his partner -- is announced. Her appearance at the top of the stairs leading down to the dance floor is taken by everyone (other than herself, the prince, and a few others) as a bit of pre-arranged theatre.

Film - Animated

Beauty and the Beast, as shown above.
Cinderella did it first.
Anastasia, at the very end.
The Kim Possible feature film So The Drama had a version with Kim on her staircase at home when she's all dressed up for prom.

Literature

Alanna and her companions do this in Lioness Rampant, but it's Thayet who really steals the show—beautiful on a normal day, when she makes her grand entrance it's a sight to stun even the most jaded.
Cat does this to Giogi in Finder's Stone, descending the staircase of his townhouse in a form-fitting dress whose neckline is described as "nowhere near the neck." Of course, she is actively trying to manipulate him and secretly working for the villain.

Live Action TV

Visually referenced in Supernatural... with a guy in a tux. Despite the guy in question being played by Jensen Ackles, he assumes he looks ridiculous. Bela, on the other hand, immediately suggests they have "angry sex" once the job is over.
Inverted in the Buffy episode "After Life", where Buffy descends the stairs in her house and Spike is rendered dumbstruck. In this case, it's because she's been dead and buried for the past 178 days.
Alternate Universe Jackie does this at her 39th birthday party in the Doctor Who episode "Rise of the Cybermen".
Fran gets a lot of mileage out of this trope in The Nanny. She makes a Grand Staircase Entrance almost every time she's formally dressed.

Theatre

Eliza makes her She Cleans Up Nicely entrance on the balcony at the top of the staircase in Higgins's study.
Dolly Levi in Hello, Dolly!, during the title song.
"Beautiful Girls" in Follies is used to introduce a parade of White Dwarf Starlets this way.

Web Comics

The Girl Genius Cinderella parody has a variation: The girl brings her own staircase.

Gil: I was most impressed with the sight of you walking down those steps.
Agatha: Oh, you flatterer!
Gil: Especially since we never had steps there before.
Agatha: Yes, well. It's always nice to make a grand entrance, no?

Snowman in the Homestuck intermission.