What are the characteristics of gothic fiction?

Gothic fiction is a part of the genre of gothic literature that initiated in response to the socio-political, psychological and philosophical context of the late eighteenth and early nineteenth centuries. The Castle of Otranto written in 1765 by the English writer Horace Walpole is thought to be the first gothic novel. Some of the chief characteristics of the gothic fiction are as follows:

• Gothic fiction is known for its preoccupation with themes of ruin, chaos, death, decay, destruction, terror, torture, etc. For example, Agnes of Lewis' The Monk is chained to a wall and tortured. In The Castle of Otranto by Walpole, Conrad dies terribly before his wedding. In The Fall of the House of Usher by Edgar Poe, Madeline is buried into a coffin.
• The gothic tradition rejected reason, clarity and rational thinking, and focused heavily on imagination, emotion and extreme passion. In a way, it approximates the Romantic Movement in literature.
• An air of supernaturalism, sublimity, mysteriousness, confusion, isolation and fogginess is seen in the depiction of the setting as well as in that of the characters. The setting could be old and abandoned castles, ruined mansions or dark and gloomy caves. The huge mansion in The Castle of Otranto by Walpole and haunted castle in The Mysteries of Udolpho by Radcliffe serve as examples for this.
• The whole work was pervaded by the fear of unknown, bizarre events and suspense. Theme of confinement or entrapment was also popular in gothic fiction. Usually, the heroine would be trapped and victimised, and seen shouting for help. For example, in Radcliffe's The Mysteries of Udolpho, Emily is trapped in her evil uncle's castle.
• Often there is a presence of dangerous villains, monsters and grotesque creatures. Mary Shelly's Frankenstein is a good example of this. 
• The work is characterised by a somber tone and vocabulary that create horror and suspense.

What are the main elements of a Gothic novel?

Gothic literature has some element of horror in it, something terrifying, spooky, or horrific. It also often has mysterious elements, sometimes supernatural or dream-like qualities. These stories often take place in a spooky, dark, confined space like an ancient castle or empty manor house, a crypt, or a damp cellar. The themes of guilt and sin repeatedly appear in gothic literature, usually in reference to some crime committed or secrets kept. 

Popular gothic authors include Edgar Allan Poe, Charles Brockden Brown, Mary Shelley, Ann Radcliffe, and William Beckford. 

If you look at the first Gothic novel, The Castle of Otranto,

"The first gothic novel is identifiable with a precision unusual in genre study. Horace Walpole began writing The Castle of Otranto in June, 1764, finished it in August, 1764, and published it in an edition of five hundred copies on Christmas Eve, 1764."

as archetype for this genre, then the following characteristics or elements define a Gothic novel.

The setting is important, usually a scarey place, like a castle or large creepy estate, like in Jane Eyre, where there are lots of doors that lead to secret rooms, locked passageways, unknown elements that exist beyond the doors create mystery and suspense.

There is a secret or a legend that binds the characters behavior.  There is a suspected curse that lingers in the halls of the domain that influences the behavior of the characters. The characters experience evidence of the supernatural, either in dreams, visions or through nightly visitations of shadowy figures who look like ghosts but are really people who in the light of day are kept hidden or locked up.

In these novels there is a sense of danger which causes heightened emotions, fear, passion, anger or panic.

The setting includes dark gloomy environment.

"most Gothic novels produce gloomy, haggard settings adorned with decaying mansions and ghostly, supernatural spirits."

The characters usually include women who are in danger or held captive in some way by a forceful male character who dominates the plot.

Think of the novel Dracula, where the figure of the vampire dominates and enslaves women.

"Gothic novels generally focus on mystery and horror, and they usually have some supernatural elements. In Dracula, the supernatural elements are many, starting with the use of a vampire as the title character."

http://www.enotes.com/dracula/style