There are a lot of elements to writing a mystery. You'll see I've included all the steps you'll need to create a story full of surprise and suspense. Read through them, and start making notes for your mystery.
Every story begins with an idea.
Keep your eyes, ears, and mind open to ideas. Try looking for ideas as you read the newspaper. Use the newspaper story as a springboard and jump into your own idea. Your main character is the most important part of your story. The main character will determine in which direction the plot will grow.