A large number of land property rights reforms, including land formalization and titling projects, are taking place around the world today. The purpose of this paper is to describe some of the expected impacts of such interventions, the challenges and problems that arise in measuring and estimating these impacts, as well as survey designs and methods for purposeful impact evaluation to overcome or ameliorate these concerns. We present a practical approach to evaluation of programs that should be accessible to non-specialists interested in impact evaluation. Using a hypothetical example of a land titling program in an urban setting we illustrate with simple visual examples how the distribution of observable and unobservable characteristics of treatment and comparison group samples might change according to the nature of the program intervention and treatment selection rules ( e.g. how the project targets geographic areas or population groups, whether and how households are allowed to self-select, etc.). This visual approach focuses attention on the key importance of survey design and data collection strategies to avoid confounding effects, and eschews a good deal of the math usually required to present these issues. Most methods for impact evaluation analysis can be explained as strategies to anticipate and adjust to these sample selection issues and as efforts to maintain a balance between observable and unobservable characteristics in treatment and comparison groups.