I can't believe I am about to make a serious response in Flood, but here goes.
I have a mild case of ADD, so for me sleeping comes easiest by allowing my mind complete freedom. Basically, I close my eyes and turn off the filter in my head. Usually these thoughts make absolutely no sense (such as a bunny with a lightsaber that is tapdancing), but the key is not to worry about controlling the thoughts and let them generate new thoughts of their own. Kinda like a nuclear reactor undergoing a meltdown.