I can't say where, when, or how often this will work, but I've tried it a few times with mixed results. If for some reason you find you can't sleep one night, indigestion, test the next day, hard mattress, too many creepy threads, whatever, close your eyes and start to play a slow and deliberate game of patty-cake. If you keep it up long enough you may start to feel a pair of something coming back to meet your hands from the void.
Congratulations, you've just summoned your first... something. I can't say it's important not to open your eyes at this point, but I didn't anyway. The first time I tried this was in my apartment when I had a presentation to give the following morning, a real toss-turn kind of night. For whatever reason I sat up and decided to put one hand out before me and I felt a faint tingle from a rather low angle. I unconsciously started to play and after a while I noticed I was humming some sort of tuneless lullaby. After about an hour or so whatever was playing on the other end, stopped and I went into a deep, dreamless, and very restful sleep.
I tried this trick again at my girlfriend's parents house while she was with me in their crappy spare bed (I was facing back to her, legs over the side of the bed, eyes closed). After about twenty minutes this time it actually felt like a pair of solid hands, from a much higher angle than before, was coming back and hitting mine a bit harder every time. Suddenly the game stopped and something made a noise in my right ear like a human shriek combined with car breaks causing me to cringe before it ran up the wall behind me into the ceiling. Maybe whatever was in that house had outgrown the game. I still slept OK. For all I know I was just hitting the wall, tiring my gullible self out and my girlfriend's just a noisy bitch but... I still can't wait to try it again the next time I can't sleep. I'm still not sure what happens if you open your eyes, though.