"Common factors" play a very important role in all forms of psychotherapy & counseling. I suggest that they're equally important in teaching meditation.
Perhaps the most detailed analysis of common factors is found in: Nancy McWilliams. "Psychoanalytic Psychotherapy. A Practitioners Guide." The Guilford Press, NY, 2004. Below is a long but valuable series of quotes from McWilliams' excellent text, which should startle meditation teachers, especially those without formal training in mental-health care. I found that almost every point (with perhaps one notable exception), is equally applicable to teaching meditation:
"People who seek psychotherapy are generally looking both for specific expertise and for the kind of relationship that will allow them to unburden themselves and grow in a more general way.
'We must not forget that the analytic relationship is based on a love of truth - that is, on a recognition of reality - and that it precludes any kind of sham or deceit.' Sigmund Freud
... The overarching theme among psychodynamic approaches to helping people is that the more honest we are with ourselves, the better our chances for living a satisfying and useful life. Moreover, a psychoanalytic sensibility appreciates the fact that honesty about our own motives does not come easily to us. The diverse therapeutic approaches within the psychotherapeutic pantheon share the aim of cultivating an increased capacity to acknowledge what is not conscious - that is, to admit what is difficult or painful to see in ourselves.
Psychoanalytic clinical and theoretical writing has always specialized in exposing motives that are not obvious to us, on the premise that becoming aware of disavowed aspects of our psychologies will relieve us of the time and effort required to keep them unconscious. Thus, more of our attention and energy can be liberated for the complex task of living realistically, productively, and joyfully. Motives that tend to be relegated to unconsciousness vary from individual to individual, from culture to culture, and from one time period to another. It is probably no accident that in contemporary Western cultures, where individual mobility is assumed, where extended and even nuclear families are geographically disparate, and where the assumed solution to most relationship problems is separation - in other words, where longings to cling are unwelcome and signs of dependency inspire scorn - psychoanalytic researchers and theorists are emphasizing attachment, relationship, mutuality, and intersubjectivity.
If this account sounds somewhat moralistic, that is also not accidental. Several decades ago, the sociologist Philip Rieff made a scholarly and persuasive argument that Freud was essentially a moralist - not in the popular sense of the person who gets a rush from attacking others for engaging in specific sins, but in the more philosophical sense of being ultimately concerned with what is true:
'... Psychoanalysis ... demands a special capacity for candor which not only distinguishes it as a healing movement but also connects it with the drive toward disenchantment characteristic of modern literature and of life among the intellectuals.'
... Psychoanalysis as a field has ... embraced an ethic of honesty that has precedence over other aims and regards therapeutic goals, including symptom relief, as by-products of the achievement of honest discourse. ... For many decades, the ethic of honesty was personified in the image of a therapist who had presumably attained unflinching self-awareness in a personal analysis and who bore the responsibility for fostering the same achievement in the patient. In current analytic writing, there is more acknowledgement that participation in a therapeutic partnership requires both analyst and patient to become progressively more honest with themselves in the context of that relationship.
... psychoanalysis is located at the intersection of two vertices: the medical and the religious. By 'medical' (Bion) referred to the more objective, rational, technocratic, authoritative stance of the person trying to offer practical help to those suffering from mental and emotional disorders. The medical vertex is characterized by validated techniques, applied by an expert, intended to have specific, replicable effects. Recent efforts ... to develop manualized treatments for borderline personality organization exemplify this face of psychodynamic practice. Current writing on the neurology and brain chemistry of subjectivity and the changes that occur in analytic therapy also belong to the medical axis. In noting the equally important 'religious' vertex, Bion was calling attention to a dimension that is often depicted as existential, experiential, humanistic, romantic, collaborative, or discovery-oriented ways of seeking answers to (unanswerable) human questions."
Nancy McWilliams. "Psychoanalytic Psychotherapy. A Practitioners Guide." The Guilford Press, NY, 2004.