Surveys are a central tool for observing and analyzing sufficiently large samples of social units at different levels of aggregation, such as individuals, households, and businesses. They require a complex methodological framework for competent preparation, execution, and analysis. Of particular importance are the quality assessment and subsequent optimization of all stages of the survey process that could negatively impact the quality of a survey. This includes procedures for evaluating and optimizing data collection instruments, assessing and optimizing sampling methods, as well as evaluating and optimizing interviewer behavior. Finally, the book also provides a brief introduction to simple and complex analytical methods for specific questions. The book attempts to explain the methodological tools of surveys.