Information about, for example, how to cite a twitter post is not yet in APA Style. Until then, you can use the recommendations from APA Styles blog.
Example from the blog How to Cite Twitter and Facebook and How to Cite Social Media in APA Style (Twitter, Facebook, and Google+)
About the blog:
"The APA Style Blog is the official companion to the Publication Manual of the American Psychological Association, Sixth Edition. It's run by a group of experts who work with APA Style every day. We publish weekly posts to talk about what we love—writing, publishing, and APA Style. We explore what APA Style is and how it works in a variety of areas, including reference citations of every sort, grammar and usage, the publication process, and social media."
In the library we have books on APA Style
Ring 0520 - 22 34 10 eller maila firstname.lastname@example.org
Chatta med en bibliotekarie - vi svarar mellan kl. 10-17 alla helgfria vardagar under vår- och hösttermin.
Phone 0520 - 22 34 10 or e-mail email@example.com
Chat with a librarian - we are avaliable weekdays between 10 -17 o'clock during spring and autumn semester.