I keep hearing about how important 'voice' is in novels, particularly YA, but I don't know what they mean by 'voice' or how to achieve it.
Can you help?
'Voice' is your own unique writing style. It is something you develop as you write and when done well can make your writing immediately recognizable as being yours, and yours alone.
Voice is not just about the way you structure your sentences and the choice of words you use, although that is part of it. Voice is also about your distinctive view of the world, and the way you choose to communicate it through language.
There is also such thing as 'character voice' which is similar, but not entirely the same. Your characters should each have their own voice, derived from who they are - their background, their location, their socio-economic group, their own sense of self. Obviously you are writing the characters, so their voices will be coming from you and your voice, but each should be recognizable as being someone different.
For example, if you are writing a dual POV narrative, a reader should be able to pick up the book, flip to any page and be able to recognise right away which of the two characters' POV we are in on that page. Even people who have similar backgrounds speak differently is subtle ways. Maybe one swears a lot while another tries hard not to.
Even people in the same family speak differently to each other. Next time you are at a family event, listen while conversation flies across the table. Take note of how people talk. Is one person dominating the conversation? Does one constantly speak over everyone else, trying to push their stories and opinions ahead of anyone else's? Does someone apologise all the time? Does someone act dismissive of anything anyone else says? Does someone else have a favorite word or words they use in the wrong way all the time?
These are all things you can use to develop unique voices for your characters. They will also inform your own authorial voice because of course, any character you write is being filtered through you and your own personality and experiences will naturally run through into your characters.
Voice is something that can't be learned because it comes from inside you, but it can be nurtured and developed. Reading a lot will help you recognise the kind of voice you like and respond to. To begin with, you may find you try to emulate the voices you find the most compelling to read - sarcastic, snarky, whimsical etc - but eventually you will find your own voice and as you write more, this will develop further and become stronger. Ideally you want someone to be able to see a piece of your writing anywhere and be able to recognize that you are the author from just a few lines.
Hope that helps!