Looking at a wall, I thought "ha, I can't see what color it is", only to realize it was actually a vivid shade of golden-yellow, feeling the color on my retinas. Impressed, I walked over toward a door with a crash bar on it, challenging once again "ok, I can never really feel anything in dreams, so I'll just have a vague sense of touching the crash bar", only to actually feel the heft of the door, and the cast steel on my fingertips.
But as I felt the crash bar, my visual sense of the scene collapsed again, as if all the processing power had just been redirected to haptic from visual. The room and the hallway were just vague ideas drawn once again from a trickle of sensory information. This was amusing enough to wake me up.
Now of course, I don't know if this was actually an insight into how the mind dreams – it's entirely possible that the mechanics themselves were something I dreamed.
The following quotes neatly sum up how flying in a lucid dream feels to me:
> There is an art to flying, or rather a knack. The knack lies in learning how to throw yourself at the ground and miss. [...] Clearly, it is this second part, the missing, that presents the difficulties. [...]
> Do not listen to what anybody says to you at this point because they are unlikely to say anything helpful.
> They are most likely to say something along the lines of "Good God, man, you can't possibly be flying!" It is vitally important not to believe them or they will suddenly be right.
Once all that happens, the next challenge is of course holding it together without waking up. That just takes practice, but some people are naturals at it I hear.
My first ever lucid dream I was about 17, and the week before read about lucid dreaming for the first time. I don't think that's a coincidence. I read about lucid dreaming, then had one. This supports the theory of thinking about lucid dreaming in everyday life in order to trigger them.
I've used the light switch thing to trigger a number of lucid dreams too, I always assumed that your brain just doesn't bother wiring things like that up, rather than the complexity of shading being an issue.
Back when I was a teenager, I got interested in the idea of lucid dreaming. One of the suggested ways I'd read of gaining awareness that you are in a dream is to habitually ask yourself if you're dreaming -- sooner or later, you'll do it in a dream.
I tried that for a while, and sure enough, I did actually ask myself if I was dreaming while in a dream, and concluded that I wasn't in dream, because I just felt sure that I wasn't dreaming! Was rather amused when I woke up and realized that I actually had been dreaming all along...
What I should have done -- as I later learned -- was to try to do something impossible while anticipating that it will happen. For example, jump with the intention of levitating, expecting to just hover in the air. Dreams work on anticipation -- what you expect to happen is what happens next. (That's why nightmares always seem to do whatever you're afraid is going to happen next; you expect your fear to come true, so it does.)
Empirically testing reality on occasion is a good thing to do; sometimes you'll find out that what you think is real is just a dream.