In survey research, the questionnaire, together with sampling, is the instrument that could make or break a research project. It needs to be sharp and effective, comprising reliable and valid indices or scales that could produce data which accurately capture the "real world" out there. It must also be paired with a representive sample to ensure that the data collected do not turn out to be a worthless heap of numbers. This course aims to share the essential "first principles" of questionnaire construction and sampling design. It will also offer tips and tricks of the trade that could enhance the interviewing experience, and thereby response rates, and contribute to producing quality data constituting the foundation of solid research or policy papers.