Refactorings are widely recognized as ways to improve the internal structure of object-oriented software while maintaining its external behaviour. Unfortunately, refactorings concentrate on the treatment of symptoms (the so called code-smells), thus improvements depend a lot on the skills of the maintainer. Coupling and cohesion on the other hand are quality attributes which are generally recognized as being among the most likely quantifiable indicators for software maintainability. Therefore, we analyze how refactorings manipulate coupling/cohesion characteristics, and how to identify refactoring opportunities that improve these characteristics. As such we provide practical guidelines for the optimal usage of refactoring in a software maintenance process.