Here are the elements for a "Gothic" tale...
To have a novel known as "Gothic," its got to follow a set of rules. First, the setting takes place in a castle, or if the story is set in America, an old family estate. That's what makes Southern Gothic appealing, because an old plantation can be used. The estate, be it a castle, mansion, or plantation, can sometimes be abandoned, or sometimes occupied. It can be near caves to augment a mystery and may often contain secret passages, trap doors, any mysterious rooms.
Next the novel has to carry an atmosphere of mystery and suspense. In "The 13th Tale," there's an atmosphere of mystery built up around the parentage of the twins, Emmeline and Adelaine. Also, there's usually an ancient prophecy involved along with omens and visions.
There are usually supernatural events which occur. It doesn't matter if they are given a natural explanation or not, the event is what's important.
Other elements include high emotion, women in distress, a powerful or tyrannical male figure and metonymies - metaphors like rain which is used to represent something else, like sorrow.
If you're thinking of exploring this genre, read a couple of books or short stories first. The plot and pacing must be "tight" for your story to be successful.
On different note:
Has anyone read "Twilight" by Stephenie Meyer? Any thoughts? I read the first two chapters so far - Bella has been Edward but his reaction to her has been frigid to say the least.