Because readers are busy and often have to make hard decisions about what reports to read and what to skim, your report will begin with an executive summary. An executive summary differs from an abstract in two respects. First, since an executive summary is intended for a busy reader, it starts with the conclusion before explaining how the conclusion was reached. (Abstracts tend to follow the same organization as the paper does: they describe the problem, review the methodology, summarize the results, and finally present the recommendations you will make at the conclusion of the abstract.)
Second, executive summaries tend to be somewhat shorter than abstracts; they should run about 10% of the length of the entire document. So if your report is 7 pages long, the executive summary ought to be about 2/3 of a page long.
The recipe for a good executive summary follows the pyramid and is as follows:
Top: Give one or two sentences saying what the report will recommend (if you're using the direct approach) or the issues the report will tackle (if you're using the indirect approach).
Body: Explain the research and reasoning upon which the recommendations are based.
Foundation: Explain (in terms that appeal to the reader's chief interests) why the recommendations should be accepted.
Click here for two pretty good examples of executive summaries.
Click here for three executive summaries to critique.