1, the purpose and scope of sampling: the purpose of sampling and the need to collect the scope of the sample. This includes a specific description of the type, source and number of samples. The purpose of sampling will have a direct impact on the choice of sampling plan and methodology.
2, the time and place of sampling: to determine the specific time and place of sampling. This includes the start and end time of sampling, and the specific location or source of sample collection.
3, sampling methods and procedures: detailed description of sampling methods and procedures, including the use of tools, equipment, instruments and so on. In addition, it is also necessary to specify the requirements for handling, labeling, transportation and storage of samples.