Write What You Know: Although Austen was already working on this story in the form of an Epistolary Novel, it was the first one she chose to submit for publication and did so shortly after her father's death—which left her, her mother, and her sister Cassandra entirely dependent on the charity of the Austen brothers. The main difference is that Austen's brothers were caring and responsible, unlike John Dashwood, but her household was still impacted when the brothers had financial difficulties.
Dawson Casting: Played straight with Hattie Morahan and Charity Wakefield, who were 26 and 24 respectively during filming. Averted by Lucy Boynton (Margaret Dashwood) who was actually 13.
Ability over Appearance: Aged up to 27 or not, Emma Thompson was far too old to be playing Elinor Dashwood — something about which absolutely no one cared one whit thanks to her flawless portrayal of the character.
Cast the Runner-Up: A curious example. Kate Winslet was initially turned down for the role of Marianne, as Ang Lee hadn't been a fan of her work in Heavenly Creatures, but she was allowed to audition for the smaller role of Lucy Steele. She pretended that she thought the audition was still for Marianne and won that part anyway based on a single reading.
Enforced Method Acting: The scene where Willoughby and Marianne shock the villagers with his wild driving was enhanced by Greg Wise's actual inexperience handling a carriage—he nearly knocked over the camera.
Hostility on the Set: Initially between Ang Lee and Hugh Grant and Emma Thompson, when the latter two made suggestions on how to film certain scenes, which wasn't done in his native country and he initially thought his authority was being undermined. This levelled off when he became used to their methods, and the actors learned to trust his instinct.
Alan Rickman finally got to play a romantic hero as Colonel Brandon.
Believe it or not, misanthropic Mr. Palmer was quite a departure for Hugh Laurie at the time, before his role in House eclipsed his popular image as an Upper-Class Twit actor.
Reality Subtext: If you look very closely, during the picnic scene you can see the briefest of flirtatious, romantic glances between Elinor and Willoughby; this is a reflection of the real-life Romance on the Set happening between the actors.
Romance on the Set: Emma Thompson (Elinor) and Greg Wise (Willoughby) met during the shooting of this film. They have been married since 2003 and have two children together, a daughter born in 1999 and a son adopted in 2003.
Separated-at-Birth Casting: Emma Thompson, Kate Winslet, and Emilie François are completely believable as sisters. Gemma Jones as their mother also falls into this, particularly with Emilie.
As Emma Thompson had never written a screenplay before, when producer Lindsay Doran approached her about the adaptation, she first suggested adapting Persuasion or Emma as a test run. What's more is that her computer malfunctioned during the process and she nearly lost all her work, but Stephen Fry of all people was able to help recover the documents.
Brandon telling the story of Beth originally was to include flashbacks, but Emma Thompson realised that it would have more effect to have Brandon just tell the events himself, and would be "emotionally more interesting" to see him struggle to reveal that backstory to Elinor.
Emma Thompson had actually envisioned real life sisters Natasha and Joely Richardson as Elinor and Marianne, but both Columbia and Ang Lee wanted her to play Elinor herself, since she had just won the Oscar for Howards End. Initially fearing she was too old to play a 19-year-old, they suggested giving Elinor an Age Lift to 27, arguing it would also make it easier for modern audiences to understand the reality of spinsterhood.
Emma Thompson, Imelda Staunton, and Alan Rickman would later appear together in the Harry Potter films, along with Robert Hardy (Sir John Middleton/Cornelius Fudge) and Gemma Jones (Mrs. Dashwood/Madame Pomfrey).