Introduce a single author's work in a paragraph and immediately follow the reference with a parenthetical reference for the year the material was published. For example: Cunningham (2008) found that only 6 percent of the children could identify a verb in a sentence. ("Cunningham" serves as the signal phrase in this example.) Follow the same formatting if the author is a business or organization (as opposed to a person).
Invoke a less favored way of crediting an author by "waiting" until the end of the sentence to make the citation: One study found that only 6 percent of the children could identify a verb in a sentence (Cunningham, 2008). This technique is less favored because it "keeps the reader waiting" for the source of the information -- never an ideal scenario.
Credit two authors in the same way that you would credit one author in an APA paper: Cunningham and Jones (2008) found that only 6 percent of the children could identify a verb in a sentence. Note the inclusion of the word "and." In subsequent references in the paper, supply this citation, but use the ampersand (&): (Cunningham & Jones, 2008).
Give credit to three to five authors in this manner: Cunningham, Jones & Sterling, 2008. In subsequent references, use only the first author's last name followed by "et al.": (Cunningham et al., 2008). Note that "et" should not be followed by a period.
Credit six or more authors with this citation: Cunningham et al. (2008). In the following references, refer to the work as (Cunningham et al., 2008).