Identifying and quantifying microplastics (MPs) in wastewater requires strict contamination control, carefully planned sample programmes, and effective pre-treatment methods. This chapter provides a comprehensive review of how MPs can be captured in various wastewater matrices. Besides large-volume and automated methods of collection that address the temporal and spatial variability of treatment systems, sample tactics are investigated regarding grab and composite sampling methods, specifically influent, effluent, and sludge samples. To ensure reproducibility and inter-laboratory comparability, field handling, transport, laboratory processing, and data validation processes are encompassed within contamination control and quality assurance/quality control (QA/QC), which are necessary safeguards against artefacts. Pre-treatment methods are vital, as they play a crucial role in eliminating MPs found in complex mixtures of suspended particles and organic debris; therefore, they receive special consideration. Different methods for evaluating efficiency, selectivity, and polymer integrity are assessed, including sieving, oxidative, alkaline, acid, and enzymatic digestion, density-based separation, oil-assisted flotation, electrostatic approaches, and combined or hybrid workflows. Combining these techniques provides a methodological foundation for accurately analyzing microplastics in wastewater. This chapter enhances the standardization and accuracy of monitoring by coordinating pre-treatment, pollution control, and sample procedures, which facilitates environmental risk assessment and the development of regulations.