A common trope, particularly in horror or thriller stories, is the throwaway character. The blonde in the tank top who wanders in the monster's jaws, the jock who jeers at the mysterious MacGuffin and promptly snuffs it. It's an excellent and easy way to show the reader that this situation is dangerous, people can and will die, and we need to take these things seriously and not push random big red buttons because they're shiny, but without having to throw anyone we really care about under the bus.

I'm not talking about the big sacrificial scenes at the end of the book, either. Not deaths that mean something - only deaths that are purely there to show the reader that this story means business. To show you that when you are infected by an alien, you die, horribly, and it's something that the characters are justified in being scared of.

But you can't just throw the lambs in wherever, or because you can't think of an easier way. There are some particular ways and means of using them that are essentially verboten, because the damage they cause to the reader's experience of the book is irreparable, especially if the character concerned hits more than one category.

It's a decision that most authors seem to make on whim or instinct - who's telling the story? The character who communicates the story to us, whether first or third person, present or omniscient, reliable or unreliable, is integral to the flavour and feeling of the story itself. Imagine Jane Eyre in first person, or Robinson Crusoe with omniscience. If Nick had been someone we could trust to tell us about Gatsby.

Having multiple characters convey your story can add huge depth to it - if that's what you want - each giving their own layer of interpretation and bias. I wrote an honours thesis about using multiple unreliable narrators as a form of characterisation, as Jonathon Safran Foer does in Everything is Illuminated. Multiple narrators allow you not only to explore the arcs of more than one person, or take the story beyond the limitations of a single vision, they can add a rich layer of complexity to the existing story.