The atmosphere will be gentle and genteel, reflecting the delicacy of Georgian middle-class life. The costumes - always rather important in a costume drama - will be understated (as much as bonnets and breeches can be understated). The make-up will be subtle. And as for sex, well... perish the very thought. Suggestive looks, playful smiles and the occasional hunk emerging from a pond in a dripping white shirt are all you should expect.
Except when you're watching the mid-80s adaptation of Northanger Abbey, that is. Because this is a version that unashamedly breaks all the rules, and is still controversial today. Here's why all Austen-ites have to see it and make up their own minds.
1. IT'S A GOTHIC THRILLER
As Jane Austen wrote it, Northanger Abbey is a satire of Gothic novels, which with their raunchy villains, spooky castle settings and panting heroines were the lurid bestsellers of their day - think Stephen King crossed with Fifty Shades of Grey. In Northanger Abbey, Catherine Morland is such a fan of all of this that she rather comically starts to think of her own life as a Gothic saga, and it's played for laughs.
But because this adaptation shows us events through Catherine's eyes, it's every bit as eerie and shocking as her own imagination. We really get a sense of her mounting paranoia as she suspects dastardly things are taking place around her. The tension is ramped up by her dark fantasies and daydreams, which give this adaptation the atmosphere of a psychological thriller. And speaking of fantasies...
2. IT'S STEAMY
The words "steamy" and "Jane Austen" aren't usually to be found in the same sentence. And it's fair to say some purists may go a bit Mrs Bennet-like with shock when they see some of Catherine's fantasy sequences in Northanger Abbey. Just to give you an idea, the very first scene shows her being literally thrown onto a bed by a mysterious man who then draws his sword, as if about to sacrifice her, while she swoons in ecstasy. Which is all a far cry from Pride and Prejudice, and there are similarly charged moments to come. Why, it's enough to make you reach for the smelling salts.
3. IT HAS A SOUNDTRACK LIKE NO OTHER
When it comes to background music, Jane Austen dramas keep it classical. You'll hear the soaring of strings, the plinking of a poignant piano, and other things that are period-perfect. But not in Northanger Abbey. If you've ever wondered what an electronic synth soundtrack would sound like in Austen-land, you're about to find out. It's almost Doctor Who-ish at times. Not only that, but some sequences feature jazzy saxophone solos, Gregorian chants, and New Age-style vocals. Rest assured, your jaw will drop, but the surreal soundtrack does emphasize Catherine's mental state. And it's completely unforgettable.
4. THE CHARACTERS ARE STARTLING
You're probably guessing by now that this version of Northanger Abbey doesn't do anything by halves. And that's very true of the characters as well. Brace yourself to meet a rogues' gallery of scoundrels and jezebels who make the likes of Mr Wickham and Lydia Bennet look positively prim by comparison.
Take Isabella Thorpe - a cunning beauty and social climber whose vibrant make-up and garish costumes make her one of the funniest, campiest characters ever to feature in an Austen drama. Her brother John is even more outrageous - a strutting would-be seducer in a flamboyantly striped suit, who is actually scary at times. Look out as well for the Marchioness, a garish character who was controversially created for this adaptation, and wouldn't look out of place in the Rocky Horror Show...
5. EVERYONE GETS WET
Whether you think Northanger Abbey is brilliant or bonkers (or a bit of both), there's one scene which really gives it a special place in the history of telly-Austen. And that's when we see Georgian ladies in Bath... actually bathing. In the Roman Baths. While fully clothed. This apparently is how it was really done, and Northanger Abbey is only Austen adaptation to actually show it happen. It's a strange and fascinating sight - rather like the rest of the drama.