Evaluation is often a required component for funded projects; however, the process of undertaking an evaluation does not always result in valuable information that can be used for learning, reflection, and program improvement. In light of methodological shortcomings and lack of meaningful use of evaluations, informal science education researchers have called for greater rigor in evaluations. To strengthen our own approach, we engaged in a process to review past evaluations and to determine a means to improve our work in this arena. A group of stakeholders first conducted a survey of our own evaluations at the museum. We identified features of the reports that were meaningful and led to useful insights about programs. We coded these guidelines in categories that emerged. Then, we conducted a modified Delphi process for reaching consensus about which guidelines for evaluation should be used across the museum to guide future work. This paper presents our final set of guidelines, a rubric for rating proposals, and implications for educators, researchers and evaluators in informal science learning spaces.