Drawing on our five years of experience developing WWC evidence standards and reviewing studies against those standards as well as current literature on the design of impact studies, we highlight in this paper some of the most critical issues and common pitfalls in designing and conducting impact studies in education, and provide practical guidance on addressing these issues and avoiding common pitfalls. This paper serves as a quick reference guide for researchers who design and conduct impact studies in education and related fields. Information presented in this paper may also help research users make better informed judgments about the quality of the research and the credibility of the evidence produced from the research. (Contains 17 notes and 1 figure.)