To become a mystery writer you should begin by reading a great deal of other mystery novels, and books in other genres, and then write your own mystery story. You might begin with a full-length novel or choose to work on short stories or even mystery poems first. If you are more interested in film or stage productions, you might consider writing a screenplay for a mystery film, or a stage play in which a mystery unfolds before the audience. Ultimately, however, to become a mystery writer who creates mysteries professionally, you will need to sell your work, regardless of what form it takes.
One of the easiest, and most enjoyable, steps toward becoming a writer is engrossing yourself in the works of other writers in the genre you are interested in. If you want to become a mystery writer, then you should read other mystery stories to get a feel for how these stories unfold and develop. You will want to find your own style and voice in your writing, of course, but knowing what others have done before can help you find those things that will set you apart and make you unique.
Then, the fun part of the job begins: writing. You will want to find whatever methods of writing work best for you. It may be helpful, as you work to become a mystery writer, to take a class or two in creative writing, to receive exposure to other writers and learn to take criticism and incorporate it into your own work. Look for writer’s workshops or groups in your area and consider joining them, not only to expand your abilities but to begin networking and forming professional contacts as well. Most importantly, however, is for you to just sit down and actually write.
Once you have told your story, the real work begins. To become a mystery writer for any industry — books, films, stage — you will need to learn how to sell your writing. This can be difficult, and you should be sure you have a fairly thick skin about your work, as you will be subject to a fairly intense amount of criticism from agents and potential publishers. You should look for an agent who represents mystery so you will find a person who is interested in your writing and will be willing to represent you in the industry.
It is also usually best to avoid agents who charge “reading fees,” “editing fees,” or any other type of fee. A few respectable and well-established agents do charge upfront, but many agents who do so are only looking to scam prospective writers. Most agents only receive a commission after they have sold your work, which means you will become a mystery writer professionally and your agent will earn his or her cut from your success.