When writing an origin myth, always remember that you are writing in order to explain a natural event. Your myth should revolve around nature in order to imitate the Native Americans' style of literature.

First decide on a natural event that you would like to explain. Examples are: why there are stars, why there are people, why there is Earth, etc.
Next create a problem. The problem should lead into your explanation.
After create your main characters. These characters should be involved in your problem and explanation of nature.
Then decide on your setting. Origin myths are greatly influenced by nature, so make sure that you consider this. Also, origin myths are fictional, therefore, you may include fictional places.
Now outline a plot. Remember, an origin myth is a fictional story, so it should contain a strong beginning, middle, and end.
Last Begin writing. Refer back to the ten characteristics of origin myths to help you in the writing process. You should introduce your characters and setting in the beginning with a lot of description. After that, you should use a lot of suspense to build up, leading into your problem. Your explanation should answer the problem as well as conclude your myth.