How do you analyse a primary source?

The easiest way to analyse a primary source (a source from the time period you are studying) is to remember the 4 Ws:

WHAT: What type of source is this? A letter, a picture, a diary entry?
WHEN: When was it written? Recently, 100 years ago, during a war or significant event?
WHO: Who wrote it? A king, a peasant, a rebel? 
WHY: Why do you think they produced this source? To inform, to persuade, to mislead?