My back (I find the ceiling to be strangely perplexing)
My tummy (I hide my face from the boogey man)
Either side (No real preference as to the side)
Specific side (Your right side - the left is for hippies)
Specific side (Your left side - I mean, all the cool kids are doing it)
I'M ALL OVER THE PLACE (Variety is the spice of life)
Other (Perhaps a combination of the common positions listed)
You're silly, Timmy (What kind of question is that, you nosy turd?)