1. Know Who They Are
This one goes without question. There's no point writing a book for children, for example and filling it full of adult themes and language. Whenever you put pen to paper (or cursor to screen!) you should always have your target audience in mind: what do they want to read? What language do they know? What themes would they find interesting? What will make them want to keep on reading? Then use this as a guide to your writing. As I'm writing a series of Young Adults (YA) books set in space I always try to think about what a teenager's reaction would be when they're reading it: What do they think of the main characters? What would they find cool? What would make them run off to their friends and tell them all about it?
2. What Subjects Do They Want To Read About?
Ever since J.K Rowling published the Harry Potter books, Children's and YA fiction has been dominated by genre books: books that feature wizards, monsters, alien worlds, and parallel universes, etc. Any author who writes for this age group has to be aware of this and dream-up suitable plots and settings accordingly. Children and YA's want to read books that are in a similar vein to what they've already read. One has only to look at Rick Riordan's Percy Jackson and The Olympians to see how much it ties in with the Harry Potter series: a realm of magic, a disadvantaged male protagonist, an absent father, a close-knit group of friends, a female character that is initially brighter and more knowledgeable than the male protagonist ... the list goes on ... this is not to say that it's a rip-off - it's just that the author has read the Harry Potter series, taken it on board, and re-packaged it in his own distinctive way to make it sufficiently original for his target audience to buy in their droves.
3. What characters Do They Want To Read About?
Again using Children's/YA fiction as an example, an 11 year old kid is highly unlikely to be very interested in following an adult protagonist - they want to read about someone who they can RELATE to - someone who looks like them, talks like them, and does the things they do. Every child on the planet can easily relate to Harry Potter and Hermione Granger because - magic aside - they are NORMAL people thrust into a magical setting over which they have no control. Deep down every child reading about Harry Potter or Percy Jackson wishes they were him, because in a way they already are.
4. What Settings Do They Want To Read About?
When I first heard that Harry Potter and the Philosopher's Stone was rejected twelve times by publishers I was amazed - what kid wouldn't want to read about a kid going to magic school? It seems like an obvious thing that a young person would be into. Now, if Harry Potter was merely camping in the rainy Lake District instead of living it up magic-style at Hogwarts, J.K Rowling's target audience might have been less impressed and as a result less forthcoming with their hard-earned pocket money. Ultimately, J.K Rowling's genius was to stir the imaginations - just like you have to - of her readership to such a degree that they talked about nothing else for eons.
5. What Plots Do They Want To Read About?
The writer's job is to create convincing storylines for their target audience and then fill it with all kinds of twists and turns that will ultimately make the reader recommend the book to someone else. Here the writer also has to be the reader: What would you find exciting and surprising? Place yourself in their shoes and then write accordingly. Sometimes the writer has to give the reader exactly what they expect (The Battle of Helm's Deep towards the end of J.R.R Tolkien's The Two Towers comes to mind here) and deliver it well, which is no easy feat, but other times the writer has do the unexpected and create new avenues for the reader to walk down. J.K Rowling did this so well with the death of Sirius Black and Professor Dumbledore in books 5 and 6 of the Harry Potter series, and the same too can be said of the infamous Red Wedding scene in George R.R Martin's A Storm of Swords. Remember you're an entertainer - so go on entertain!
6. How Do Other Authors Do It?
A good writer is also a good reader. To write successfully for your target audience you also have to read around a lot and see how other authors do it. For example Stephen King, one of the greatest writers of our time, reads between 70 and 80 books a year. Now, I don't get anywhere near that myself - I'm not a professional author with 7 days free to both read and write - but I do read for at least 1-2 hours every day. Reading keeps the writer aware of their target audience and what books they are prepared to pay money for. At the end of the day it's an investment not just in their future, but also yours too. So go on read a book!
7. Get Some Feedback
Okay, so you've finished your book. Now you must get some of your target audience to read and review it. What do they think? What do they find interesting? What do they find uninteresting? How do they think you can improve it? What do they think of the key characters and the main plot points? etc etc. Once you've finished soliciting their opinions, use them as a guide in the editing process until you arrive at a final draft that your target audience will accept and hopefully fall in love with.
If you want to read my novel - Jack Strong and the Red Giant - about a bullied, 12 year old boy's adventures in space check out the link below: