A best practice is a technique or methodology that, through experience and research, has proven to reliably lead to a desired result. Use these recommended practices for writing code relating to systems where safety is critical.
How often should this be used?
Ad hoc as required.
Developed from the 'The Power of Ten -- Rules for Developing Safety Critical Code,'' IEEE Computer, June 2006, pp. 93-95 and this spinroot.com article