Deepening one's understanding of personality psychology requires understanding the standard research methods employed in the field. These research methods are various. An increasing number of serious treatments of procedures and methods on the web are accurate and accessible.
The Types of Data Sources Used in Personality Psychology -- This portion of this web site explains the many different kinds of data that can be employed to study personality psychology, as organized within the Systems Framework for Personality Psychology.
Comparisons of Peer-Judged and Self-Judged Persoanality Attributes -- The peer-nomination project by Thomas Oltmanns and Eric Turkheimer examines the differences between data gathered on a person by him or herself, and through the use of observers. This sophisticated project tries to tease out the difference in meaning of the two, and when one or the other type of data is preferable.