It's important to question your primary sources, as a first step to evaluating them for accuracy, bias, and usefulness.
Questions to ask:
- What: What is this source? What are its physical characteristics?
- Who: Who wrote this letter? Who took this photo? Who preserved it?
- When: When was this source created? When was it discovered, or published? (Consider 'when' questions also in terms of the context of the event you are researching, too.)
- Where: Where was this created? On the battlefield or safe at home?
- How: How did this source come to survive? How is it presented - was it published or re-published? was it edited?
- Why: Why was this source created? Is it a personal letter or diary, or was it created by the government? Was it created in the process of doing business?
The answers to these questions may be obvious, or less apparent, but considering them will help you determine the authenticity of the source, as well as discern any bias in the sources.