According to epistemology, there are four main ways of getting knowledge:
1. Empiric knowledge. This is the knowledge obtained through our senses and through experiments.
2. Rational knowledge. This is the knowledge obtained through logical thinking and considerations.
3. Aesthetic knowledge. This kind of knowledge comes from appreciation of beauty of creation and arts.
4. Knowledge gained from authorities. This is knowledge gained from teachers, books, mass media, and so on.
Since modern people have no way to check everything through experiments and logic, they learn most things from authorities. Cult leaders use this fact for recruiting and indoctrination. They present themselves as authorities and people tend to believe them and uncritically take the information gained from them.
After leaving cults, ex-members need to restore their capacity of independent thinking. This means that they need not just to take everything that authorities say, but to use their logic and sometimes their experience to check this information. Of course, it is impossible to check everything. However, I believe that it is necessary to do that in the matters that are important for them.