Needless to say, I was a bit different as a child. I was a loner, often wandering off, getting lost, or just zoning out from what was happening around me. Though I had no words for what I was experiencing, in retrospect, I know I was feeling bored and drained by what I took to be a sort of pointlessness or fatedness to life. At some point, I found I could, and thus did, alter my consciousness, though at the time, it seemed I was just doing what I naturally would do.
There were these were naturally-occuring states caused by changes in brain chemistry. The dream-state is one example of such an altered state. It quickly occurred to me that the dream state was a door to a magical realm of infinite possibilities, one that would inspire my waking imagination to conjure up new fantasies and philosophies.
There was the classic "headrush." Getting up too quickly after a long period of rest, the vision clouds up with colorful dancing patterns, consciousness dims, like when one is about to fall asleep, and fainting is a definite possibility. Not the safest, but it allowed one to dance along the edge of consciousness.
Then there's spinning in place to induce dizziness. Never one of my favorites, because the dizziness would often make one fall down, and the accompanying nausea can induce vomiting. A tale is told of my childhood in which I as a toddler was repeatedly spun on a spinning chair until I finally tossed my cookies. Perhaps this experience turned me off to the dizzying and nauseous effects of spinning, and for that matter, alcohol.
Hyperventilating was another, that had sort of an opposite effect: your heart would race, head throbbing, and you seemed extra-conscious for a bit, although it could quickly turn to unconsciousness too.
The best one, I discovered while innocently rubbing my eyes. I found a certain spot on my closed eye that I could push on, that would cause a strange yellow light to appear in the corner of my vision. I now know I was perturbing some mechanism of my eye that caused this phenomenon. Continuing to push on it would cause this light to spread over my entire field of vision. Then what appeared to be a twisting tunnel would appear, and it seemed my consciousness was passing through it. At some point, the tunnel would widen out to this "place" of brightly colored geometric patterns, swirling and morphing in front of me. I had already encountered the idea of other worlds of existence, from things I had read like the Chronicles of Narnia, or the Oz series. At some point, this coalesced into a belief which I held, and I searched for those secret doors to fantasy realms with the utmost sincerity. I recall vividly my disappointment and frustration at not finding them in physical reality. But here in the privacy of my closed eye, with the swirling lights and patterns, I was king, and my stimulated imagination was able to pick out images from the visual chaos to represent the various elements of the fantasy world: elves, goblins, dragons, weapons, armor, etc. which I'd also encountered in the game world of Dungeons and Dragons.