Detective Work
Primary sources, archival research, is the lifeblood of history. Historians work with surviving documents, in whatever form, to create interpretations of past events. When historians approach primary documents it is with a series of questions that help us understand the documents and see patterns that explain events.
A lot has been written about how to evaluate a primary source. A Google or Duck Duck Go search will get you many good results. Of course, you can dig dipper into this with more advanced reading, so for the students in my classes this is meant as the starting point not the end all be all.
If you want to follow up now, here are some videos that will help.
Khan Academy
How to Read a Document Part 1 (context and setting)
How to Read a Document Part 2 (textual analysis and exploring the source)
American Historical Association
What is "historical thinking"? Historian Jim Grossman
Phillip Payne (That's me)
This is really about asking questions.
Author - Providence
Who wrote the document? What do we know about the person?
Does the author have a point to make? An ax to grind? Is the author making an argument? If so, what is it? Why?
Is the author credible?
Presentation
What can you tell from how the document reads? Is it a formal document? A legal document? Someone's diary? Was the person well educated?
Context
What context did they write it in? Where did they write it? Who was the intended audience? Why did they write it?
What else do we know? Does the information in the document line up with other information? Check other primary documents and secondary literature?
How is the context different than yours? Words and ideas might not have the same meaning. The author was living in a different place, culture, and time.
Evaluation
Are the facts accurate? Why? An author might be trying to deceive or mislead the audience, but it could also be that the person living in the time lacked information.
What is missing? Sometimes, what we forget is as important as what we remember.
What do other sources tell you?
Patterns
Relate the document to other points of information. How does it fit into the books you are reading? Your general understanding of the context? Does it fit a pattern or not? Why?