Although there are a number of them

Although there are a number of them, all guidelines follow a few basic principles:
Manufacturing processes are clearly defined and controlled. All critical processes are validated to ensure consistency and compliance with specifications.
Manufacturing processes are controlled, and any changes to the process are evaluated. Changes that have an impact on the quality of the drug are validated as necessary.
Instructions and procedures are written in clear and unambiguous language. (Good Documentation Practices)
Operators are trained to carry out and document procedures.
Records are made, manually or by instruments, during manufacture that demonstrate that all the steps required by the defined procedures and instructions were in fact taken and that the quantity and quality of the drug was as expected. Deviations are investigated and documented.
Records of manufacture (including distribution) that enable the complete history of a batch to be traced are retained in a comprehensible and accessible form.
The distribution of the drugs minimizes any risk to their quality.
A system is available for recalling any batch of drug from sale or supply.
Complaints about marketed drugs are examined, the causes of quality defects are investigated, and appropriate measures are taken with respect to the defective drugs and to prevent recurrence.