Headings clarify your logic and organization for the reader by establishing a hierarchy of sections in the paper. The most important thing to keep in mind is that "all topics of equal importance have the same level of heading throughout a manuscript" (APA, 2010, p. 62).
Note that title case means only the first letters of words with four or more letters are capitalized, while all other letters are left lower case. Sentence case means that only the first word of a title is capitalized, while all other letters are left lower case.
Use Level 0 heading (or title heading) formatting for the References heading of your reference list.
Here is the formatting for all APA heading levels:
Title [Level 0 heading: centered, not bolded, title case—also used for References heading]
Introductory paragraph(s) go here. Paragraphs are indented a half inch from the left margin. Do not justify the right margin. Also remember to double-space your lines throughout the document. In course papers, there is no need to include an Introduction heading above these introductory paragraphs (see APA 3.03).
Level 1 [Centered, Bolded, Title Case]
First paragraph(s) of section go here
Level 2 [Left-Aligned, Bolded, Title Case] Paragraphs of section go here.
Level 3 [Tabbed .5 inches, bolded, sentence case, period]. Note that the first sentence of the paragraph in this section begins on the same line.
Level 4 [Tabbed .5 inches, bolded, italicized, sentence case, period]. Note that the first sentence of the paragraph in this section begins on the same line.
OASIS