In the Bhakti-rasamrta-sindhu the science of devotional sevice is explained as follows:
In the beginning stage there must be a preliminary desire for self-realization. This will lead one to the platform of desiring to associate with spiritually advanced persons. The next step is to become initiated by an authorized spiritual master and to perform devotional service under his guidance. Through the execution of devotional service under the guidance of the spiritual master, one will become free from all material attachments, achieves steadiness in self realization and finds taste in hearing about Krsna, the Supreme Personality of Godhead. This taste leads one to further attachment in Krsna consciousness which is called bhava or the preliminary stage of pure love of Godhead. Pure love to the Lord is called prema or the supreme perfectional stage in life.