First, you need to decide exactly what type mystery you are planning to write. Hopefully you’ve read enough crime novels (seems to be the preferred name for the genre these days) to know what kind of novel you are going to write. To name a few: the private eye novel, amateur detective, usually someone with an interesting or unusual profession, can be hard-boiled or a cozy, the police procedural, romantic suspense, woman in jeopardy (think Mary Higgins Clark),
historical mysteries–can be a combination of any of the above, thriller, when an innocent becomes involved, either by accident or coincidence, in dangerous events beyond his or her control (think Alfred Hitchcock movies), suspense, when the protagonist is in a constant and increasing state of danger.
Mysteries of earlier times were more interested in the hero solving the crime, now are as interested in the emotional impact of the crime of the hero and his or her private life. You have to create a credible protagonist to help the reader suspend disbelief. Though you must know the back story of your characters, you don’t necessarily have to tell it all. Bits and pieces should come out–maybe internally. Don’t lump it all together in one place. Don’t forget the villains–they should have history and issues also.
Here’s a check list of what you need to know about the book you’re going to write:
Scene of the Crime
Suspects and Motives
Where everyone was at the time of the murder; alibis.
Conflict that led to the crime
Conflict that follows the crime and leads to the solution.
Climax, the emotional high point of the novel.
Solution or resolution
Remember it’s not necessary to only write about what you know, but what you don’t know, you need to find out about.
Use your imagination, create unusual characters and interesting settings, either real or ones you’ve made up.
Once you’ve finished, print the manuscript out and go over it carefully. Make sure you tied up the loose ends and things progress in a logical manner. After that, have someone else edited it for you, someone who knows how to edit–preferably someone who reads and understands the mystery genre.
And yes, you can do something different as long as it works. My latest book, Smell of Death, is a police procedural, but there are several crimes in the book that must be solved. In this particular series, I wanted to show how the job affects the family and family life affects the job.
Smell of Death is authored by F. M. Meredith, a.k.a. Marilyn Meredith, available at http://fictionforyou.com and Amazon.com