"Sources are people talking to other people." Doug Downs
Who wrote it? A journalist? An academic scholar? A person who has expertise of some sort?
When was it written? What effect does its age or currency have on its value to you?
Why was it written? What audience did the author have in mind? What are they trying to do with this document - persuade, inform, further our knowledge by publishing new research findings?
Where did they get their information? What evidence do they present? Do they explain the sources of their information?
How did they arrive at their conclusions? Did they use appropriate methods to get there? Did they misunderstand anything or leave something important out?
What have other people said about this topic? How does this source fit in with the larger conversation?
Quite often you will be expected to use "scholarly" or "peer reviewed" or "academic" sources. How can you tell whether a source is scholarly? Look for these indicators.
Though many databases let you limit a search to scholarly or peer reviewed articles, those limiters aren't foolproof. As an example, they will include book reviews, which are not reporting original research. Take a look at "Anatomy of a Scholarly Article" from North Carolina State University Library.
Peer review means the source has been reviewed prior to publication (usually without the reviewers knowing who wrote the source and vice versa); reviewers will then recommend if the work should be published. Many - but not all - scholarly sources have been peer reviewed. To check if your scholarly article has been peer reviewed, you can visit the journal's website.
Each group will have three sources to look at (a book and the two links or PDF files below the book). Be prepared to discuss these questions:
Sources have different functions for your research (BEAM)
There are different authors of information
There are different audiences for publications
There are different packages for information