This document gives guidance on the determination criteria for when laser diffraction is the most appropriate method for the analysis of samples, the appropriate preparation of samples, the verification of the correct functioning of instruments, the interpretation of data, and the assessment of data quality. This document focuses on the practical steps needed to obtain results of good quality, rather than on theoretical considerations, and covers not only the measurement of solid particles (in wet and dry measurement configurations), but also emulsions and bubbles. Result variation expectations of real samples are also considered in this document.