"Just because you're my sister, it doesn't give you a right to lecture me about mum's deteriorating health conditions that have become worse following that ill-advised break in Corfu that you took her on with your husband and kids."
"I'm going to the lab, where I'll perform an assay using agar filled plates to find antibiotic resistance, utilising techniques invented by Alexander Fleming (1881-1955)."
Both of these are examples of exposition done badly. The first is people telling each other things they already know. The second is an info-dump that's probably been copied verbatim from Wikipedia. So what is exposition? Exposition is information that an audience needs to follow the plot. It is also a difficult thing to deal with when writing a script - especially if you write it like those two clunkers at the top. And writers - all writers - always struggle with how to do it.
Obviously, the Austin Powers films dealt with it brilliantly - and head on - by having a character called Basil Exposition whose every utterance involved explaining the plot. But, chances are, you'll have to find a more subtle way of sprinkling exposition into your script. Like coincidence, exposition happens in real life quite happily - with people sometimes telling each other things they already know or people explaining things at length. But in a script, it doesn't ring true because it feels too convenient. So once again - like writing 'realistic' dialogue that is actually 'stylised realistic dialogue' - writing must straddle the line between what feels real and what is actually real.
So here are six ways of handling exposition...-
Have a barny. If two characters can have an argument - or some sort of conflict - then it is a good way of drip-feeding information. The way to do it effectively is to allow the audience to learn about how the characters cope in a given situation - with the secondary goal of getting across the expo information. So the audience will be more intrigued to wonder why Fiona doesn't take life seriously - than they will to hear that Fiona is ignoring her responsibilities in caring for her sick sister. The two things happen at once - one is character, one is exposition. Together it sugar coats the exposition and makes it palatable.
Tease it. Make the exposition something that the audience is dying to know. This is used in horror films - what is the creature stalking our party of teens? - but it works for any other genre too. By the time you share the information, the audience will be keen to lap it up. So set up mysteries in your scripts and pay them off at the best possible times.
New kid. Introduce a character who is new to the world - and that way he/she can be told everything they (and the audience) need to know. A recent example is The Hobbit- which does this when Bilbo Baggins gets his mission. Note that Bilbo isn't new to the world of Middle Earth, but the idea of the quest and his companions is new to him and us.
I've called you here because... In some cases, the only way is to have a scene where the characters are briefed on the situation. Most action and spy movies do this. Don't be shy of doing this, but try not to make it too long or one-sided. Star Trek Into Darkness does it well - presenting a briefing scene that turns out to be an assassination attempt, wrong-footing the audience while still delivering some expo.Predator starts with an exposition scene but it's entwined with two characters meeting again after years apart with their old rivalry resurfacing.
Do it anyway, but distract the audience. If you watch a film like The Terminator, there is a lengthy exposition scene when Kyle Reese explains the whole back story to Sarah Connor. It could be turgid and dull. But it works brilliantly because at the same time we see a lengthy and exciting chase sequence as Sarah and Kyle race to escape the Terminator; struggling to re-load a shotgun as the machine approaches etc. If you can distract your audience and spin two plates at once - exposition and action - then this can be a good technique to get the information across.
Voice Over. This can work in small doses. Pacific Rim gets its whole origin story out of the way in the pre-credits sequence thanks to a brooding voiceover explaining everything. This leaves you the rest of the running time to enjoy that set up. And those five minutes could so easily have been the whole movie - mankind fighting the monsters and then in the final act using a Jaeger for the first time and being victorious. But no, instead the film showed confidence and made the origin story a starter to the main course (I live in hope that superhero movies will take note so I don't have to sit through yet another Spider Man / Superman / Batman origin...)In general, while the techniques above may be useful, there is actually a better technique that you should try first. Cut, cut and cut. See if you can cut what the audience needs to know. You may realise that some of the information you want to include provides texture, but that it is not essential to the audience's understanding. Cut it out. See what the bare minimum is to get things across. And the added bonus of doing this is that the audience may have to work to fill in the gaps. And audiences love to work.