The first thing a prospective mystic must do is to consciously reject promissory materialism. Like any sort of faith, this will take some time as the roots of ideologies with which we are raised run deep and wrap themselves tightly around all of our other beliefs and assumptions such that we will run into internal obstacles (cognitive dissonance, etc.) which will have us wanting to fly to the extremes of either tossing out the whole garden to be rid of the weeds or else being so daunted by the process of disentangling the invasive vines from everything else that we throw our hands up and leave the whole garden to strangle.
Many today would not consider materialism to be a faith, but they forget that faith and belief are fundamental to the human mind. No matter how much we may rail against any particular idea or ideology, we are never without faith in something. Promissory materialism is the default religion of the academy, certainly, and of much of broader global civilization as a result. It is belief in the narrative of scientific progress — not of genuine science, science-as-method, but of science-as-dogma. Its priesthood is the physicist, the cell biologist, the popularizer. The promise is of a different, wholly material heaven in which Reason roots out all superstition — and, by implication, all religion, all culture, anything which cannot be upheld by numbers. This is not a problem with science as such, and the hard physical sciences do not actually support materialism any better than they support most other specific metaphysical positions. (There are many philosophers and scientists who think that it does quite the opposite, in fact being a better support for various forms of Idealism, nondualism, and so forth, but that’s a different topic.) The ultimate promise is that eventually there will be no more “consciousness” to worry about; it’s all matter, so the mind doesn’t matter. But if subjectivity itself doesn’t exist, who is saying so? All of that to say: faith is essential even to those who denigrate faith.
The very function of mysticism, whether it be Yoga or something else, is to demonstrate that faith need not be blind. It may at first be blinkered, but perspective can be widened by the very subjective experience which materialists tell us isn’t real (but from which their whole edifice depends). Yoga is itself a form of promissory faith, but one whose promises can be realized at least to some extent in this very lifetime by any interested individual and not in some far distant future either in the next world or the next generation (or the generation after that, or the one after that, or the one after that… as materialism’s promises keep being pushed back by each new discovery of the ultimate weirdness of the cosmos). But faith in what, exactly? Many are attracted to Yoga because it does not contain a catechism of dogma which must be accepted for salvation. It does, however, contain teachings (dogma in its original sense). These teachings have proven true for generation after generation.
Yoga and Tantra recommend faith in God, but they also recognize that many people coming in the door will not be able to muster it and that’s all right. You have to start from where you’re at, not some hypothetical ideal starting position. If you do not have faith in God, the Gods, the Good, and so forth, have faith in your teacher; if you do not have a teacher, have faith in the teaching. That doesn’t mean that you have to believe everything your teacher says, nor everything you read in the Yoga Sutras, Siddhasiddhantapadhattih, Vijnanabhairava Tantra, Dhammapada, or anywhere else. Instead, put enough trust in the methods described therein and in your own capacity to give it an honest try. Know, of course, that it will take time and work to begin seeing any of the promised results, but such is the case with anything according to the scale of the goal sought.
It is therefore sometimes good for the mystic to take the approach of the magician, seeking after tangible and (at least somewhat) repeatable results which though not the Goal at least point to its possibility and make it seem nearer. For this (though not only this) reason, Tantra does not shy away from operative sorcery which sometimes resembles witchcraft. Not all Tantrikas are sorcerers, but it is there for those who need it. Not only can it provide material aid to those in real need of it — like any “spirituality of the people” — it can allow the practitioner to more or less directly encounter some of the specific claims of Yoga in their own lives. This sort of experience permits faith not only to deepen, but also to broaden, to become more inclusive of other ideas and experiences.