Select a time in American History for some context.

Choose the subject for your story - something that happened in that time and place.

Create some crazy characters and try to make each one have a definite purpose in the story.

Using characterization, start building the plot. 

Try to keep the pace of the dialogue snappy, the scenes short and the drama high.

Try and link it to the AHS universe.

Choose a setting for your story, something that will make a good backdrop for events.

Do some research about the era.

Pair characters with actors that would fit best or pick an actor and create the character to suit them. 

Make sure there is more than one antagonist (two at the least) and throw in some unlikely friendships.

Have plenty of references to urban legends, historical characters, and classic horror movies.

Finally, have a resolution to the story that makes sense.