If font size and style are not specified by the organization for which you are writing (e.g., publisher, university), the suggested font is 12-point Times New Roman.
For more details see the APA Style website:
All information and page number references are based on the 6th edition of the Publication Manual of the American Psychological Association (2009/10).
Need a copy of the Publication Manual? Click here for details. See Also: APA Style Guide to Electronic References, Sixth Edition