Many engineering approaches exist that are widely accepted as 'good design practices' for their ability to deliver high-quality conceptual schemas. Such schemas are supposed to be stable enough for subsequent system exploitation, and flexible enough to accommodate future changes. This paper presents a comparative review of a dozen current engineering approaches as to which mechanisms they employ to enhance flexibility of the CS. No single best strategy emerges from the analysis. It is found that most engineering approaches employ only a limited number of mechanisms to enhance flexibility. While strategies may be combined to yield better flexibility for the CS, it is unclear which combination works best under what conditions. Whatever the current engineering approaches have to offer, a designer is still largely dependent on good judgment and personal expertise to obtain a stable CS.