Create characters we'll love. Think of a few of the most famous sleuths of all time: Nancy Drew (sweet and innocent), Jessica Fletcher in "Murder, She Wrote" (comforting grandma type), Columbo (quirky but brilliant) and Tom Sawyer (bold and mischievous). These characters are colorful and unconventional.
Determine the type of story you want to write. Mysteries, at their core, are puzzles. They can entail anything from the search for missing treasure to uncovering a secret in one's past. There are many sub-genres under the umbrella genre of mystery, but whether you opt for the traditional amateur-sleuth approach of Nancy Drew and the Hardy Boys or the ghostly goings-on of R.L. Stine, understanding the conventions of the genre is key to success.
Devise clues sufficient enough to allow your readers to play along, but clever enough to challenge them. The star of the mystery is the "whodunnit?" factor. Plotting your story before you begin writing is an essential step in the process.
Plotting a mystery is like cutting pieces for a jigsaw puzzle. The pieces need to fit together in order to create the whole. Answer these three questions to plot your story effectively:
1. What is the mystery?
2. Who solves the mystery?
3. What are the key clues to solving the mystery?
Plant clues cleverly but fairly. Balance is essential. Too many obvious clues and your story becomes predictable; you risk sending your readers away bored. Planting too few clues, or clues made available only to your main character, cheats your readers. Always allow readers access to the same information pertinent to solving a mystery that your lead sleuth has.
Write a great ending. A mystery should never be solved magically. The reveal should come as a result of the clues leading to the conclusion of the story. Writing mysteries for younger readers takes skill and hard work, but if you're willing to learn the conventions, lay the groundwork and treat your audience fairly, you'll find great rewards in this genre.