Use sensory detail
All five senses – sight, sound, touch, smell and taste – can be effective in creating a strong atmosphere. All you have to do is make sure you're using the most effective sense for the feel you want to create.
Want to give a creeping sense of unease? Think of the taste of rot as you bite into a strawberry or the sudden, cloying scent of blood when you're daydreaming on a packed bus. Or maybe a sweet, magical feel? Think of the golden gleam of sunlight catching in your eyelashes when you blink, or a song familiar from childhood just at the edges of your hearing. How about a melancholic ghostliness? Think of a quick channel of freezing water as you lie back in a hot bath.
You don't have to go through a laundry list of details for every description – pick a few well-chosen details, and sprinkle them through your writing. It's all about creating a vivid world for the reader to inhabit.
Hold an image or word in your head as you write
I love creating story mood boards – in Ye Olden Days of the 2000s I did this with scraps cut from magazines and newspapers and pinned onto a corkboard, but now it's 2015 and we have Pinterest(this will open in a new window). When I sit down every morning to work on a story, I have a quick scroll through my mood board to get myself in the right frame of mind (here's(this will open in a new window) my mood board for The Gracekeepers).
If you don't think in visuals, choose another sense: a song, word, phrase, scent or memory that evokes the atmosphere you want to create. There's no need to describe the image or use the word: it's about holding it in your head as you write.
Inhabit your imaginary world in your daily life
As much as you can, choose the media you consume as you're writing. You're not doing this to directly take any plot elements, characters or details – you're trying to keep yourself in the right head-space, so that when you sit down to write, the atmosphere of your story feels strong in your imagination.
If you write to music, make sure it fits the tone of your story. Perhaps pin some relevant pictures to your desk, or change your desktop background to an image that creates the right feel. If it's possible to choose your physical surroundings – for example, to walk on a deserted beach as you write about isolation, or wander in a museum as you write a historical story – then do take a day or even your lunch hour to do this. You'll only be able to create a strong atmosphere for your reader if you can feel it yourself.
It isn't always possible to have control of our listening or viewing material when we have to consider the choices of our family, friends or workmates, but even small things can help.
Limit your imagery
One minute you're comparing something in your dystopian world to a rotten apple; the next minute there's an industrial pipe; then a labyrinth, and an insect, and a sunbeam, and a temple, and reality TV, and a stovepipe hat, and – you get the point. Piling on visual metaphors randomly will give a muddled, inconsistent feel when you really want a strong, coherent atmosphere.
Choose two or three themes or ideas that seem relevant to your story – for example, perhaps it's a story of redemption and so you'd like to use ideas of religion and portals. Or it's a love story and you'd like to explore ideas of discovery and old-fashioned sea voyages. Try to ensure that your visual details and word choices are in some way connected to these central ideas. This can become cloying if it's overdone, but used subtly it's an incredibly effective way to build atmosphere. (By the way, you might not be able to choose your themes before you start writing, as your story will develop as you write – don't worry, as your word choices can be changed and your imagery streamlined when you edit).
Focus on the language
Atmosphere isn't only about description. Consider carefully every word you write to create the atmosphere of your story.
Trying to create a sense of unease or confusion? Play with syntax, vary sentence length, use more unusual word choices, pepper in some sentence fragments. Want the reader to feel soothed and happy? Use more straightforward sentence structures, and – while never resorting to cliché – stick to more traditional word choices.
Pay attention to the lengths of your words, sentences, paragraphs and chapters. All of these can affect the pace and feel of your story. It's all about experimenting: play around with your language to see which matches the atmosphere you want to create.
Some of these suggestions might seem odd, but give them a try! Choose one technique from this list for the next story you write. And let me know how it works for you.