Ernst, J. A., Monroe, M. C., & Simmons, B. (2009). Evaluating Your Environmental Education Programs: A Workbook for Practitioners. Washington, D.C: North American Association for Environmental Education.
Observations are used to gather more information on how a program operates. By having someone just observing, instead of leading the programming, they can be attuned to how program staff are doing, how participants respond to activities, and more. You must prepare to do a quality observation in the same way you prepare to do a good interview, or two implement a survey. For example, you typically produce an observation protocol, or guide, so that you limit the specific activities you observe to a reasonable number, and so that you are consistent each time you do an observation. The PDF linked below provides more guidance on conducting observations, and a checklist for creating your own protocol.