Professional historians—people with some advanced training in the discipline of history—bring a particular and often-misunderstood set of skills to the task of learning about the past. They gather and weigh different kinds of evidence, including primary sources (documents or recollections from the time period being studied), material artifacts, and previous scholarship (secondary sources). Using these sources, they work toward careful, often provisional interpretations of what was happening and why at a given time. [from National Council of Public History]
The term historical method refers to the collection of techniques and guidelines that historians use to research and write histories of the past. Secondary sources, primary sources and material evidence such as that derived from archaeology may all be drawn on, and the historian's skill lies in identifying these sources, evaluating their relative authority, and combining their testimony appropriately in order to construct an accurate and reliable picture of past events and environments.
Source criticism (or information evaluation) is the process of evaluating the qualities of an information source, such as its validity, reliability, and relevance to the subject under investigation.
Gilbert J. Garraghan and Jean Delanglez divide source criticism into six inquiries:[1]
The first four are known as higher criticism; the fifth, lower criticism; and, together, external criticism. The sixth and final inquiry about a source is called internal criticism. Together, this inquiry is known as source criticism.
Source: Historical Method