While some crime stories or mysteries have the criminal or victim as the main character, most of the time we see things through the eyes of the person investigating the crime. Detectives come in all shapes and sizes. They can be police professionals, private detectives, clumsy amateurs, witnesses to a crime, ordinary people, insurance investigators, etc.

Character plays a majorly important role in the Crime/Mystery genre. Fans of this genre often describe the characters as real people and reading about their favourite detective is often described in the same way one would talk about spending time with a friend. Readers often prefer protagonists like themselves; detectives whose gender, education, class, background, occupation, etc. reflects their own. The subjectivity or personality of the protagonist will even overshadow the importance of a good plot.

The definition of a crime is 'an unlawful activity for which punishment is imposed upon conviction or a violation of morality'. Crime fiction or mysteries typically revolves around a crime, often a murder, which seems impossible to solve. This seemingly unsolvable crime sets things in motion and throws the story down a path to somehow find out what happened. Sometimes the crime takes place on the page, and other times the characters only discover the aftermath. The crime is the heart of the story, and its seemingly unsolvable quality hooks the reader and the protagonist. It becomes the driving force of the book.

The term ‘red herring’ refers to a clue or piece of information which is or is intended to be misleading or distracting. Red herrings can be scattered throughout your novel to keep the reader from guessing the culprit of a crime or explanation of a disappearance too soon. They escalate tension and suspense and make a novel more riveting.

Suspense can be a sub-genre on its own but it is also an important element of a mystery/crime novel. Suspense is the element that makes the reader uncertain about the outcome. Suspense can be created through almost any element of a story, including the title, characters, plot, time restrictions and even word choice.

Another means for creating suspense is to use the objective viewpoint in which the story is told, not through the mind and feelings of a major character, but only by what he says and does. That character may have some secret that affects the outcome of the story, but since the author never tells us what the character thinks—or remembers—but only what he says and does in the present, the viewpoint adds to the suspense. The reader wants to stay engaged as an impending event is gradually unfolded, suspense is present in all good fiction.

A mystery novel is typically more teleological or 'end-focused’ than a novel in another genre (such as high fantasy). In mystery novels, everything should build up to a satisfying answer to primary questions such as ‘Who? Why? What?’