Once you have defined your research question, identified your target population, and assessed your resources and constraints, you can start searching for potential research sites that meet your criteria. You can use various sources and methods to find and evaluate potential sites, such as online databases, maps, directories, literature reviews, expert consultations, site visits, and pilot studies. You should compare and contrast the advantages and disadvantages of each site, such as the accessibility, representativeness, suitability, and reliability of the data and participants. For example, if you want to study how people use public transportation in a city, you could compare and contrast: How easy or difficult is it to access and communicate with the participants at each site? How well do the participants at each site reflect the diversity and characteristics of your target population? How appropriate and conducive is the physical and social environment at each site for your research methods and tools? How trustworthy and valid is the data and information that you can collect at each site?