The process of assigning requirements to releases is difficult and release planning methodologies are becoming increasingly complex in an attempt to take into account different stakeholder perspectives and criteria. However, there is a need to focus on understanding the criteria used in release planning in order for the methodologies to adequately support this process. This paper specifies the criteria for software developers to use when planning releases by operationalizing the risk criterion and enhancing the interdependency criterion. A controlled experiment was conducted to evaluate release plans created with this new versus an informal methodology. The results imply that the criteria specified in this new methodology are in fact used by developers in the creation of releases. After further testing, this methodology could prove beneficial in helping developers create release plans for large numbers of requirements.