1. Start with characters in a certain situation.

Your characters can be going about their lives in a perfectly normal manner, when some inexplicable event happens to turn their lives upside down. What is this event? Why can it not be readily explained?

You can introduce locked rooms, locked boxes, locked cupboards; strange letters or maps; disappearances of one or both parents linked with the appearance of strange guardians or disliked relatives; sinister neighbours; strange lights and noises at night; uncharacteristic behaviour in a sibling or friend; strange behaviour by pets; friends who suddenly turn against the main character for no apparent reason; something is stolen… start jotting down lists of ‘mysterious’ events and you’ll end up scribbling for pages as your imagination takes over.

2. What are the characters prompted to do about this event? Why is it important that they do something about it?

Build the elements of mystery as the story progresses. Let’s say, for example, that Character comes home one day and finds that Mum has had to go away unexpectedly. Character is not too concerned about this — Mum has a job that takes her away at short notice occasionally and she always arranges for Aunt Joan to come in. But this time, Aunt Joan doesn’t come. Instead, strange Uncle Bret is there. He is evasive about why he’s there instead of Aunt Joan. He’s evasive about the whereabouts of Character’s mother. And when Character sneaks out to phone Aunt Joan, there’s a recorded voice saying that the number’s been disconnected.

 When you introduce elements of mystery, don’t pile them all in at once. It’s more convincing to let things build up. Let the main character become more and more suspicious. Structure your story so that nothing seems to add up. Then, when Character finally confronts Uncle Bret and demands to be told where his mother is or he’s going to the police, have Uncle Bret hint at danger to his mother if word gets out… and you’re away. Before you know it, you’ll have your young reader staying up until all hours of the night to find out (a) what’s going to happen to Character, and (b) where on earth Character’s Mum has got to.

3. In the above plot outline, you can see that solving the mystery is of the utmost importance to the young protagonist.

What could be more threatening than to have a beloved parent disappear, and a sinister, scarcely-known relative to be put in charge? Whatever your story line, the main character must desperately want to solve the mystery.

4. Start thinking of possible endings.

You don’t always have to know the ending when you start plotting. It’s often better if you don’t.    If you can surprise yourself, you’ve got a good chance of surprising the reader. Let’s look at the above scenario again. We have two possible paths to follow for Uncle Bret — he can be a Bad Guy, who is collaborating with someone else in the disappearance of Character’s Mum, or he can be a Good Guy, who is there to try to find out where his sister has gone without alarming her children.   Perhaps he is afraid if they know too much, they’ll be in danger too.

If Uncle Bret is a Bad Guy, why is he in the house? Is there something he needs to find? Does he think Character might know where it is? And what has he done with Character’s Mum? When you’re plotting the ending, don’t always think of the obvious. Experiment with several different endings, and see which one would give the reader the most pleasure because of the twists and turns of the puzzle.

5. Make your hero or heroine proactive.

He/she has to try desperately to solve the mystery him/herself (perhaps with the help of friends) even though he/she doesn’t know much to start with. Have the main character overcoming obstacles and danger through his/her own intelligence and bravery. He/she should be interesting. He/she should be likeable. He/she should also make mistakes now and again — perhaps mistakes that almost end (or DO end) in disaster.

6. Keep the action moving.

You should have genuine clues mixed in with red herrings. ‘Bury’ the genuine clues in other action — action that seems more important than the clue at the time — so the reader glosses over it. (Well, you hope he/she’ll gloss over it, anyway!) You don’t have to slot these clues in place in the first draft. Often, when you’re writing the story, you’ll think of a different plot twist and you’ll realise you need to insert a clue back near the beginning of the story. Fine. Go back and do it. There are plenty of mystery writers who start from the end and work backwards. They find it easier to plot that way. (For example: Decide where Character’s Mum is; why she’s there; who put her there (or told her she had no choice but to go there) and work backwards from there, putting all the clues in place where you’ll need them.)

7. Send the main character off in the wrong direction once or twice, or have him interpret a clue the wrong way, or even fall victim to one of the red herrings.

There may be smaller mysteries along the way — solve these before the end. The main scene should involve solving the main mystery. Build suspense by feeding the reader (and, perhaps, the main character) a little bit of information at a time. Have someone refuse to divulge essential information.

8. Play fair with the reader.

This means not planting clues that lead nowhere, or making a big deal about a letter or a phone call that is ultimately explained away by someone collecting for a charity or some such thing. Readers will feel justifiably annoyed. By the end of the story, everything should be explained.

9. Give your mystery an exciting title — one that hints at secrets and mystery and adventure.

The kind of title that makes children reach for your book before any other. Some made-up examples: The Day My Friend Went Missing; The Wildcat Mystery; Secrets At Dark Bay House. 

Do you want spark a child's imagination?

Develop a full time career or part time hobby as a children’s writer. Writing stories for children can be a enjoyable income earner, with a lifetime of royalties.