Primary sources provide first-hand testimony or direct evidence on a subject. They are created by someone who experienced the period or event first hand. Because they are eye-witness accounts, many primary sources are created at the time the event occured, but recorded memories -- such as autobiographies, memories, and oral histories -- are also considered primary sources.
For more examples see What are Primary Sources (Yale University)
When evaluating primary sources, ask yourself these questions:
From: UCSC University Library, Distinguish Between Primary and Secondary Sources and SUNY Empire State College Library, How To Evaluate Bad Statistics and Research Methods.