Metagenomics offers the possibility to study the microbial community of soils at large scale, allowing the characterization also of unculturable microorganisms. Availability of high-quality DNA is a prerequisite of this approach. However, since soils have highly heterogeneous physicochemical properties, several parameters need to be considered for the development of the best molecular practices. A method for isolation of high-molecular-weight and good-quality metagenomic DNA from different soil samples is described here. The protocol combines physical and chemical strategies to ensure efficient cell lysis and precipitation of humic impurities-free DNA suitable for downstream processing for metagenomics study.