I'm pretty sure initiation rituals artificially heighten the likelihood the initiate will remember that moment vividly (as a flashbulb memory), then introduce concepts or beliefs that the initiatory tradition wants to pass on.

A big one is non-identification with the self, and the radically different state of mind this leads to. Sam Harris' book "Waking Up" explains this decently, entirely without and explicitly against supernaturalism.

Apart from that, I think the storehouse of spiritual techniques has been looted fairly exhaustively. Some things have been found to work in some way (astral projection as lucid dreaming, amulets as comfort objects, various beliefs in mind-altering speech as hypnosis and NLP, various forms of meditation as techniques of relaxation and improved cognitive control) while most have been found to be nonsense. I can't think of any the jury is still out on, except the two above.