The oldest - which I think I've been using as far back as my pre-teens - is to close my eyes and picture myself on some sort of invisible vehicle travelling along a mountain road at quite high speed. It always begins on the road in the mountains, as I can see the sheer sides of the crags sweeping up away from me - but once I've started moving the landscape around me changes. Clearly my imagination is at play, but I have absolutely no surface awareness that I am consciously changing my surroundings - it all just appears to flow naturally, and once I'm out of the mountains the landscape will change apparently of its own accord; forests, moorland, river valleys, fields, riversides, back to the mountains - it all just sweeps past me as if I'm on a real journey.