Service-to-Self (STS) means to think about the self 95% of the time.
Service-to-Others (STO) means to think about others 50% of the time.
What is generally considered evil most often corresponds to STS. The terms are however laden with a baggage of subjectivity and what is bad for one can be good for another, thus these are easily misleading. The polarization to either STO/STS cannot be reduced to an external code of ethics only.
The Service-to-Self orientation is not so much a choice as a failure to progress. Where an entity in the Service-to-Other orientation is repeatedly choosing to include others as the focus of their concern, the Service-to-Self entity has never left their original focus - the self. Thus, the evolution, during spiritual growth, into two paths is natural, a factor of uneven growth rates, and the resulting separation of the orientations during early densities is simply a practical step taken to facilitate learning. A Service-to-Self entity cannot be forced to develop concern for others, nor can this concern be worn like a social facade in the densities above 3rd Density, as a fake or a sham. Where entities are given free will, as all are within God's Universe, such a choice as the Service-to-Self orientation is and will continue to be a reality.