Statistics is the science of data collection and data analysis. We provide, in this chapter, a brief introduction to principles and techniques for data collection, traditionally divided into survey sampling and experimental design --- each the subject of a rich literature. While most of this book is on mathematical theory, covering aspects of Probability Theory and Statistics, the collection of data is, by nature, much more practical, and often requires domain-specific knowledge. And careful data collection is of paramount importance. Indeed, data that were improperly collected can be completely useless and unsalvageable by any technique of analysis. And it is worth keeping in mind that the collection phase is typically much more expensive that the analysis phase that ensues (e.g., clinical trials, car crash tests, etc). Thus the collection of data should be carefully planned according to well-established protocols or with expert advice. We discuss the basics of data collection in this chapter.