Adopting agile practices brings about many benefits and improvements to the system being developed. However, in mission and life-critical systems, adopting an inappropriate agile practice has detrimental impacts on the system in various phases of its lifecycle as well as precludes desired qualities from being actualized. This paper presents a three-stage process that provides guidance to organizations on how to identify the agile practices they can benefit from without causing any impact to the mission and life critical system being developed.