The abstract is almost always the first section we read in a research report.  As such, it should provide valuable information about what is included in the remainder of the report.  According to the APA manual, the abstract should be no more than 150 words in order to provide enough information about the paper without replicating large sections.  In other words, a good abstract will include, in general, one or two sentences for each of the following: (1) Statement of the problem; (2) Brief summary of the literature; (3) Brief Summary of the methods used in the present research; (4) Brief summary of the results found in the present research; and (5) The significance of the present study and/or need for further research.