This is a very powerful question. There is not a direct or easy answer to it. The nature of the question strikes at the very basis of human identity. Cults and psychological manipulation attempt to offer an answer to the question that drives so many human beings: Who am I and what shall I do?
In my mind, the reason why cults flourish is because there is a lack of questioning. Cults advance because individuals are told to willingly submit to an individual or organization that possesses all of the answers to an individual's predicament. The element of mind control is of vital importance in being able to connect to an individual. A cult offers an alternative that provides "all of the answers to the individual." I think that one way to avoid this is to ensure that one's ability to ask questions is critical. Being able to propose questions and live with the consequences of those answers is essential in avoiding cult situations and scenarios in which psychological manipulation is evident. The cult predicates itself on providing unifying answers to divided forms of consciousness that can prove to be appealing. Individuals who ask questions and continually probe without a blind acceptance can do much to avoid falling into such a situation.
I think that this element reveals another attitudinal approach to avoiding cults and psychological manipulation. Cults find success because they provide totalizing and unifying answers to being in the world. They advocate they can provide reason and purpose in a world that might be lacking it. In a larger sense, cults succeed because they strive to provide a unifying answer. Individuals who succumb to cults or psychological manipulation demonstrate a weakness towards that type of answer. They possess a craving for unity, symmetry, and totality. Perhaps, one way to avoid cults is to avoid this craving for totality. It requires individuals to shift their thinking away from a "perfect" answer and accept a realistic or simply "good" one. When we shift or thinking from a sense of absolute perfection and accept the realistic conditions in which we live in the hopes of simply making it better, the appeal of cults seem to decrease. The element of mind control and psychological manipulation can be minimized when individuals are not predisposed to immediately embrace theories where complete perfection is preached. In his book, The Book of Laughter and Forgetting, Milan Kundera pointed to the condition that craves totality as one that has underscored what it means to be human:
… an idyll for all. People have always aspired to an idyll, a garden where nightingales sing, a realm of harmony where the world does not rise up as a stranger against man, nor man against other men, where the world and all its people are molded from a single stock and the fire lighting up the heavens is the fire burning in the hearts of men, where every man is a note in a magnificent Bach fugue and anyone who refuses his note is a mere black dot, useless and meaningless, easily caught and squashed between the fingers like an insect.
The cult or notion of mind control in psychological manipulation is rooted in the appeal to this "idyll." This "garden" is the appeal that drives a cult. The "realm of harmony" is the allure of a cult, and the world in which "all its people are molded from a single stock" brings individuals harmony where disharmony might have been present. It takes a shift in thinking to recognize that these appeals might not have form the basis of individual identity. Perhaps, individuals might not be able to find a sense of complete and totalizing happiness, but that there can be a sense of contentment apart from the controlling aspects of others and organization. When individuals make this shift in thinking, I think that one can avoid cults and psychological manipulation.
Finally, I think that individuals must maintain individuality in the face of conformity. The cult is the ultimate expression of conformity and "group think." Cults don't function well when dissonance and the voice of dissent is evident. Rather, the success of the cult is evident when individuals submit, and give up their individuality for something larger. In all of the worst cults, there is this lack of individual identity towards "the cause" or "the leader" or "the group." When individuals cherish their condition as individuals, refusing to submit it for anything, cults can be avoided. Individuals who act as individuals and not as conformist are primed to avoid cults and psychological manipulation.
Just about anyone an fall prey to some forms of manipulation, but what makes a cult successful is to focus their efforts on those who may be most vulnerable. In the case of finding new cult followers, vulnerability lies in their desperation for answers, for acceptance, for social connections, or for meaning. Those who already have a strong self-identity are less likely to be swayed into a cult, just as those who already feel full-filled by a religious/spiritual path are less likely to look for answers in other avenues. Of course, knowing how to recognize the patterns and red flags associated with the psychological manipulation surrounded by cultism is always a good way to keep safe.