When evaluating information, it is useful to identify if it's a Primary or Secondary source. By doing so, you will be able recognize if the author is reporting on his/her own first hand experiences, or relying on the views of others.
A first person account by someone who experienced or witnessed an event. The original document has not been previously published or interpreted by anyone else.
One step removed from the primary original source. The author is reexamining, interpreting and forming conclusions based on the information conveyed in the primary source.