A good haunt will have a great storyline to work with.
This was from the finest haunt in California. Much of the storyline is derived from the environment, using the original 1928 market place building at the last remains of the first vineyard in California, the Guasti vineyards. The train also comes by every half hour which figures prominently into the storyline as well.
You will also want to try and avoid basing on released horror movies and media icons. 1. Intellectual laziness. 2. They get sue happy.