An author can use descriptive language to quickly establish the mood and tone of a gothic story. This can be used to include different techniques such as similies, metaphors, and personification. Describing the Gothic scene firstly helps to establish the scene and tone of the writing as it starts the story - and describing the setting can also link to the tone of the piece.
The main themes in Gothic literature include death, isolation, and darkness. So keywords involving these themes would help to set the tone.