There is a good tutorial presented by the American Psychological Association, which anyone who is not already very comfortable with all aspects of APA style should watch.
View the "Basics of APA Style" tutorial online.
For more experienced users of APA style, there is also an APA tutorial on what's new in the 6th edition (new as of July 2009).
View "What's new in the Sixth Edition" online.
The tutorials linked above are created by the American Psychological Association, and hosted on their website.