Marine microbiomes play a crucial role in oceanic ecosystems, influencing biogeochemical cycles, climate regulation, and marine biodiversity. Accurate characterization of these microbial communities requires standardized protocols for sample collection, processing, sequencing and data analysis. This chapter provides a comprehensive guide to essential methodologies for marine microbiome research including field sampling strategies, DNA and RNA extraction techniques, high-throughput sequencing approaches (such as 16S rRNA amplicon sequencing and metagenomics) and bioinformatics pipelines for data interpretation. Additionally, we discuss quality control measures, best practices for reproducibility, and challenges associated with marine microbiome profiling. By adopting standardized methodologies, researchers can generate reliable, comparable datasets that enhance our understanding of marine microbial ecology and its broader environmental implications.