Screenwriting

In order to write a screenplay, you need to be an expert in your plot, as well as your characters. Thus you need to "do your homework" or conduct research about what you are writing, whether it's a historical bio-pic or a contemporary story. And by researching a diverse range of people, your characters will be more diverse (and not just several copies of yourself or your close friends and family). Delving in the research will not only make your screenplay more authentic and compelling, but also will spur your creativity. 

There is no such thing as too much research. Hopefully you will be sucked in to the sources you find, with one source leading you to others. But you don't want it to be an excuse to not writing your screenplay.

Go as Close to the Source as Possible

The most useful sources are going to be primary sources or first-person accounts: interviews, letters/diaries, photos or footage from the time period, etc. Are these sources objective? Quite the opposite. But the idea is to get as close to "in the head" of your characters.

The next most useful are nonfiction works grounded in research: historical works, sociological studies, etc., ideally written by researchers or possibly journalists, but that's not an absolute requirement. The less "academic" the text, the less objective and balanced the text will be. That doesn't make it a bad source, just a less balanced source. And the more "academic" texts tend to be, but not always, more dry. 

Need to brush up on a historical event, famous person, geographic area quickly? Try encyclopedia entries -- Wikipedia but also ones the library has purchased that have gone through a solid editorial process. Search the EWU Library Catalog and limit your results to the format Reference Entries. We have several hundred encyclopedias online.

Feature Film Examples

1950s Korea

• I'd look for nonfiction books about the Korean War, but focused on Koreans. (I hope you can read Korean...)
• I'd look for collections of letters or oral histories of Koreans alive then. (Ones in Summit in English are about 1 person rather than interviewing several. See Korean War, 1950-1953 -- Personal narratives, Korean)
• I'd watch documentaries about the Korean War. One that does discuss Koreans (vs only Americans) is called Our Time in Hell, and of course our copy is "missing". Will need to request in Summit.

Medieval World-Building

• How realistic we're you thinking of the story being? I would suggest picking a culture to be at least a model (Viking-like vs. feudal knights, etc.), then look for nonfiction books on that culture. (Or you could take pieces from this culture and that culture.) True primary sources will be limited to folklore (Viking Sagas) and a handful of medieval tales (Chaucer, Mallory, etc. for Europe).
• I'd look for medieval art books, or art books for that time period.

1980s LGBT & HIV/AIDS

• I would suggest focusing on one major city (SF, NYC, etc.).
• I'd look for nonfiction books, oral histories, maybe newspaper accounts

Post Office

• Which city? Timeframe?
• Historical books about working at the post office??? Labor & Politics in the US Post Office, Merit System & Municipal Civil Service: A Fostering of Social Inequality, There's Always Work at the Post Office : African American Postal Workers and the Fight for Jobs, Justice, and Equality

Mexican Immigrants

• There are lots of individual memoirs of immigrants from Mexico. You could narrow by timeframe of when a person immigrated, male/female, adult/child. This one is more of a collection of personal narratives, versus just one person's story. This is another that combines an academic study with interviews, aka an "ethnographic study"
• There are several Kanopy videos with the term undocumented in the description. (Link will only work on-campus. Or log into another database before clicking on this link.)

Pilgrims

• If you want to incorporate some historical accuracy to your story, I would look for non-fiction books about the Pilgrims. Nathaniel Philbrick's book Mayflower is a good one, in that it's aimed at a general audience, while still well-researched.
• You can find collections of writings by the colonists, or a smaller collection that Nathaniel Philbrick compiled and explains. They are old enough to be digitized, but then I would double-check against a more authoritative version.