This document is a guide that presents a series of 37 questions aimed at assisting buyers of online samples for market research. It covers various aspects of sample sourcing and recruitment, including the experience and capabilities of the service provider, the types of services offered, and the methodologies used for participant recruitment. The guide emphasizes the importance of understanding the sources of online samples, the validation processes employed to ensure participant authenticity, and the overall management of sampling projects. It also addresses data quality and compliance with relevant data protection laws, highlighting the need for transparency in sample composition and the measures taken to maintain participant satisfaction. Additionally, the document outlines the significance of adhering to industry standards and best practices in order to facilitate effective market research.