I usually sleep in the nude with my ass sticking straight up in the air. Extremely bad for my neck and back, but who cares! I also sleep with my phone underneath me. I wake up in a puddle of drool almost every morning.
I wait for the sun to touch the horizon, and then smack my bed as hard as I can with my right hand. Most of the time I'll slowly descend into a black haze while seeing occasional flashes of text, and before I even know I'm asleep I'm awake and standing at the side of my bed again.
On my stomach usually. I can sleep on my side, but only with someone else or a large pillow there. When I try to sleep on my back, I start thinking big thoughts, sometimes end up in existential rage. I can sleep very well sitting up though.
That depends on where I'm sleeping, mostly. If I'm on the couch or downstairs in my single bed I tend to sleep on my side and maybe on my stomach from time to time. If I'm upstairs in the queen bed I like to sleep on my back, I think because the mattress is more comfy up there.
However, last weekend I got a sunburn because I was out at the Renaissance Festival. It was all across my shoulders and upper back, so I've been forced to sleep on my stomach since because it's still burning and hurting ><