There are but few textbooks that deal with selection and selection procedures, particularly with the use of a predictive measure. Be it for the recruiting or reassignment of personnel, admission into educational programmes, qualification in sports, even quality control for factory-made products, many procedures are available whose mathematical bases are little known or publicized. In this essay, we tackle a collection of such procedures, in four categories, explaining them in a friendly and narrative manner and with an example drawn from the personnel management domain.