Research is rarely ever well-achieved in a straight line
Become familiar with resources available on your topic
Log your keyword strategies when searching databases and the web to minimize search replication in:
Primary and secondary resources work hand in hand to help inform understanding of an historic person or event. Their efficacy in informing your research can overlap. Educated guesses are often necessary but must be based in exhaustive research using as many viable resources as possible.
Primary resources are direct links to the past including original documents, artifacts or accounts produced by a creator/witness in close space and time to the person or event. In the purest sense the source is in its original form--not condensed, interpreted or evaluated.
Secondary resources are based in commentary, analysis or description outside the time and space frame of the historic person, creation or event.
Tertiary resources help organize and locate secondary and primary resources