After decades of trouble falling asleep, I've found a simple technique that works for me. The goal of this technique is to replace words/monologue with images in your stream of consciousness. I do this by picturing three shapes, each engulfing the previous one. Start with a sphere. Just imagine a sphere and nothing else. Then picture a 5 sided pyramid that perfectly engulfs the sphere so that the sides are tangential. As this happens the sphere shrinks so the pyramid takes up the space of the sphere. Then repeat, but with a cube. So the cube encompasses the pyramid, with the bottom planes the same and the 4 upper edges intersecting with the 4 upper corners of the cube. Then shrink that and put it in a sphere, starting the process over.

I've found that when I'm really tired I have no trouble conjuring this imagery and sometimes within just a few cycles, vivid explosions of color will flood in and I go to sleep. Other times, I struggle to picture a sphere and start off with the 2d equivalents - circle, square, triangle. The whole thing is a bit like counting sheep, but that never worked for me.