Here is a checklist specifically of things to think about:
Does the study:
a. Represent all benefits and costs?
b. Inflate, or to the contrary, understate, some benefits or costs?
c. Conduct sensitivity analyses or otherwise qualify results appropriately in view of uncertainties?
d. Accurately measure net-changes from well-defined baselines?
e. Clearly describe the accounting domain?
f. Consistently specify the accounting domain?
In terms of format, break down subsections with headers, bounded with an Introduction and a Conclusion. In terms of writing style, it is IMPORTANT to use the active voice as much as possible.