Distinguish primary from secondary sources, evaluate credibility with a who/when/why check, and set up a running source-tracking log.
A primary source is created at the time, by someone directly involved -- a laborer's letter, a photograph, a newspaper account from that year. A secondary source is created later, analyzing or synthesizing -- a historian's book written decades afterward. A strong paper needs both: primary sources supply firsthand evidence, and secondary sources supply context, analysis, and connections one document alone cannot offer.
Check every source with three questions: Who wrote it (authority)? When (currency)? Why (purpose -- to inform, sell, or persuade)? Track sources as you find them, not after, in a simple log: source name, type, key information, and a credibility note. A log built in real time means nothing gets lost or needs re-finding later.
Mastery looks like: They sort sources into primary and secondary, apply a who/when/why credibility check, and maintain an accurate source-tracking log.
Common stumbles: Relying only on secondary sources, or accepting a source without checking who wrote it and why.