What type of lifestyle, or life circumstance, or race, or sex, or physical appearance most leads one to either the Service-to-Self or Service-to-Other orientation? Incarnations are chosen by the birthing envoys based on the particular lesson or lessons the entity is most in need of learning, but the incarnation can bring unexpected influences to bear. One formerly leaning in the Service-to-Other orientation, finding themselves born into wealth and a beautiful body, may be lured by the ease with which they can make demands on others into considering the Service-to-Self orientation. On the other hand, this entity may take advantage of the avenues open to one born into wealth to do service to others on a major scale, and good looks only used as a door opener in this regard. The choice is up to the entity, solely. One formerly leaning to the Service-to-Self, finding themselves born into the weaker sex and unattractive at that, may find themselves empathetic to their former victims and regretting their behavior in former lives. On the other hand, this entity more likely will choose to make themselves as unattractive as possible, taking a rebellious stance, and bully anyone in their vicinity weaker than they as compensation. Again, the choice is up to the entity, solely.
Crises, such as major disasters like earthquakes or hurricanes, offer opportunities for action that help the 3rd Density make their spiritual orientation decision. As you say, actions speak louder than words, meaning that words can lie, but the actions a person takes demonstrate their true intentions. In a major disaster, choices must be made, as bleeding bodies and the screams of agony are everywhere. When one turns away from the bewildered, bleeding toddler and takes oneself to comfort and safety, one has made a clear choice.
But life offers these kinds of choices every day, in less dramatic ways, and the circumstances one is born into make little difference. Take the choice a wealthy young man must make between taking a job that will gain him the approval of his family and friends, or one that will allow him to make a difference in the world. He will lose some of his creature comforts, in the form of family and friends - his security blanket. How much different is that from a poor man, relying on his extended family, who risks alienating them if he emphasizes the big picture rather than the short term financial gain. In both cases the security blanket is being risked, and the loss is measured in relative terms. To one used to wealth, not being invited to join the yacht club is equivalent to not being included in a game of billiards, and having to downgrade one's standard of living by moving out of the big house and into a flat is equivalent to moving out of a crowded bedroom and using the back seat of the car for a bed. It's all relative, and the spiritual lessons proceed in spite of differences in life circumstances. In all cases, what is done with the incarnation is up to the entity, solely.