Purdue University Online Writing Lab - Although this website has started to utilize advertisements and pop-ups, it's still probably the best APA resource online. 

There are some free citation management software applications that assist with organizing and exporting citations. Such applications although helpful, do operate on a garbage in/garbage out principal. Those applications are:

• Zotero
• Mendeley
• EndNote

In-text Citations are the citations that happen within the body of your paper. Here are some different ways to create in-text citations.

One work by one author
Example:

Quimby (2000) compared monorail systems

In a recent study of monorail systems (Quimby, 2000)

In 2000, Quimby compared monorail systems...

One work by multiple authors
When a work has two authors, always cite both names every time the reference occurs in text.
Examples:

As Smithers and Burns (1993) demonstrated..

...as has been shown (Smithers & Burns, 1989)

When a work has three, four, or five authors...
Cite all the authors the first time the reference occurs.

In subsequent citations, include only the surname of the first author followed by et al. (including the period)
Cite the year if it is the first citation of the reference within a paragraph.
Example:

Hibbert, Rivera, Monroe, Foster, Zweig, and Colossus (1994) found
[Use as first citation in the text]

Hibbert et al. (1994) found
[Use as subsequent first citation per paragraph thereafter]

The reference list (or reference section) of your paper contains a list of all of the resources that you cited. Here's some things to keep in mind when creating a reference list:

• Arrange the list alphabetically by the last name of authors.
  • In the reference list itself, give the names of all authors. Optionally, if the paper has more than six authors, the rest may be abbreviated to 'et al.'
• Two or more articles by the same author (or authors) are listed chronologically.

Citing Journals

Example of Journal Article Citations (with and without DOI)

Schematic of a Journal Article Citation

Citing Magazine Articles

Citing Books, Bulletins, or Reports

Examples of Book, Bulletin, and Report Citations

Schematic of a Book, Bulletin, or Report Citation 

Citing Chapters Within Edited Books, Bulletins, and Reports

Examples of Citing Individual Chapters within an Edited Book

Schematic of a Chapter Citation Within a Book, Bulletin, or Report

Example of a Reference List Utilizing Multiple Types of Resources