This chapter outlines the methods and techniques used for sampling marine primary producers. The primary focus is on introducing and discussing sampling techniques for phytoplankton, macroalgae, benthic algae, and coral reefs. Phytoplankton sampling typically involves the use of plankton nets, water pumps, and bottles. For macroalgae, benthic algae, and coral reefs, traditional techniques such as quadrants, transects, snorkeling, SCUBA diving, and video recording are employed. Additionally, innovative optical methods are also used for coral reef sampling. The selection of the sampling method is based on the study objectives, habitat characteristics, and logistical constraints. Combining multiple techniques enhances the reliability of data. The chapter aims to provide a comprehensive overview of the current state of marine sampling and monitoring. It also compares the advantages and disadvantages of different sampling methods while addressing the challenges and implications of monitoring marine ecosystems in relation to human activities and environmental changes.