Q. How can I tell if an article or book online is peer reviewed?

Here is a video that explains the difference between a scholarly (peer reviewed) article vs. a popular (commercial or trade) article:

http://youtu.be/VeyR30Yq1tA

More information on this topic can be found here: 

http://guides.lib.uh.edu/content.php?pid=121273&sid=1043105

Most academic databases such as Academic Search Complete have an option for limiting searches to "Scholarly (Peer Reviewed) Journals." Look for the checkbox in the section "Limit Your Results."