Think about your favorite murder mysteries, as well as your least favorite ones. What do you love and hate about this genre? What is important to you? Answering these questions will help the direction of your novel. Sit down and write a one- or two-page summary of your plot. Take that short summary and use it to create a longer outline. Some writers like to write each scene in an outline while others go chapter by chapter.
Write your first draft, based on the outline that you have created. Do not feel that you have to stick exactly to the outline if you find your story carrying you in another direction. Complete your draft without editing or rewriting. Many writers become bogged down in making every sentence perfect and never finish the novel. Write the entire novel first. Wait for at least two weeks and then reread everything that you have written. Begin to correct mistakes and revise sections that need to be stronger.
Find a way to foreshadow the outcome of your mystery without giving it away. In a successful murder mystery, the reader is left thinking, "Why didn't I figure that out?" The answer should be obvious but only after it is given away.
Find a friend or fellow writer you trust to read your murder mystery and provide feedback. This beta reader should be someone you can rely on to give you real criticism instead of just praise. Continue to rewrite and revise your novel until you are satisfied with the results.
Create the protagonist for your story. Your main character or sleuth should be an intriguing and well-rounded person. Many of the greatest protagonists in murder mysteries have demons in their past. These problems should motivate their actions and also cause difficulties as they try to solve the murder mystery.
Decide who committed the murder. What are the motivations of your antagonist? How does he or she hide the crime? Like a good protagonist, an antagonist should be a well-rounded character. The murderer in many crime mysteries isn't actually revealed until the end of the novel, so they must have positive characteristics or the ability to fool the other characters.
Find a connection between the two. Why is your protagonist involved in the murder? What motivates them to find the killer? Frequently, the main character and villain are similar characters who have taken two different roads. Think about what your main character has in common with the murderer that will make your novel more intriguing.
Start your first chapter with questions that need to be answered. It is important to hook your reader in the first few pages with a suspenseful story and compelling characters. Murder mysteries often begin with the murder or a short build-up to the crime.
Make sure your protagonist has a compelling reason to want to solve the crime, but let their flaws interfere. Every real person is flawed and your characters should be as well. Your main character should be struggling against the murderer and himself to solve the puzzle and bring the novel to its conclusion.
Give your characters the constraints of time, money or other urgency. If they have all the time in the world to solve the problem, you lose the suspense and importance. What could go wrong if the murderer is not revealed?
Write action scenes with short sentences. Short sentences can speed up the pace of a novel because the reader can skim through them faster than long sentences. Action scenes with a fast pace have a natural urgency and suspense that will draw in the reader.