The Writing Center at University of Wisconsin-Madison has a practical online resource for helping writers do APA citation accurately. 

What I like about this site:  features a podcast and a printable PDF overview, yet the most day-to-day valuable may be the online templates for managing different kinds of sources. 

Check it out: APA Documentation

The Center for Writing has reference books, handouts, and carefully selected online resources for multiple documentation styles, including AAA, AP, APA, ASA, CBE / CSE, Chicago / CMS, and MLA.

For a printable list of recommended resources:  documentation-style

The University of Aukland’s Referen©ite won the 2007 Outstanding Academic Integrity Resource Award — and for good reason.  It has excellent student-friendly presentations that explain why citation is so valuable.  It also has tools that walk writers through the steps of the referencing process.  There’s much more to this welcoming, up to date, and well-researched resource. 

Here’s what the creators say about it:

The main purpose of Referen©ite is to encourage students to correctly reference the sources they use in written work. To do this, it:

• Promotes the meaningfulness of the practice: it is not mere institutional compliance - the values at the core of the practice are shared across cultures;
• Provides tools and information to make correct referencing sources significantly easier - to virtually eliminate any excuse that it is too difficult or confusing.
• Provides 24/7 access to referencing information via a single simple url (www.cite.auckland.ac.nz); through the site’s own content and also by acting as a central ‘hub’ for excellent online referencing resources.

Highly recommended!