An abstract should be a brief summary of the paper's primary premise and findings, no more than 120 words.
For the abstract page, center the word "Abstract" at the top of the page, and then include the abstract for the paper, double spaced, and flush against the left margin.
Here's a condensed version of what the APA Manual (12) says about abstracts:
An abstract is a brief, comprehensive summary of the contents of the article; it allows readers to survey the contents of an article quickly. . . The abstract needs to be dense with information but also readable, well-organized, brief, and self-contained.
. . . Ensure that the abstract correctly reflects the purpose and content of the paper. Do not include information that does not appear in the body of the paper. If the study extends or replicates previous research, note this in the abstract, and cite the author and year.
. . . Comparing an abstract with an outline of the paper's headings is a useful way to verify its accuracy.
. . . . Abstracts should not exceed 120 words. Begin the abstract with the most important information (but do not waste space by repeating the title). Include in the abstract only the four or five most important concepts, findings, or implications.
An abstract should report on, rather than evaluate, the content of your paper -- do not add to or comment on the content of the paper.