Por: Samuel Canchaya Moya, catedrático en Universidad Nacional de Ingeniería y Pontificia Universidad Católica del Perú. Gerente General en SAMPLING OK.AbstractGood sampling provides data that, combined with good geological information, allow us to raise arguments to reject or drill a prospect, to invest or not, to classify a tonnage as waste or economic mineral, or to decide whether a domain is or is not contaminated by harmful elements.In general, a sampling chain can be divided into primary sampling, secondary sampling (comminution), and chemical analysis. The largest known biases and errors are introduced at the primary sampling stage, which are several orders of magnitude higher than those made during secondary sampling and chemical analysis. However, QA/QC procedures, widely used today, focus primarily on secondary sampling and chemical analysis. This is best demonstrated by applying only "twin" or duplicate samples to primary sampling, which is approximately two percent of the total control samples; the remainder are applied to secondary sampling and analysis.These bad practices were highlighted by the author, from 2010 until his last participation in the Muestreo 2018 event. This paper not only discloses that reality, but also documents the most important advances in sampling best practices and QA&QC, which have placed Peru at the top of the world ranking in sampling practices.