I sleep just to the right of center or on the right completely. I’ve done this my whole life since my beds were always against a wall on the left when I was younger. Now that I have a big bed in the center of the room, I still favor the right side. The head of the bed is always on the right, as seen from the door, as well. Nothing if not a creature of habit, I am.
I sleep on the left side of the bed when hubby is home on weekends. I sleep in the center of the bed when he’s away during the week.
Right side when facing bed. Like many couples, we’ve never switched sides. Wouldn’t feel right.
On the side that’s farthest from the telephone or alarm clock. In my current bed, that’s the left.
I sleep on the left side facing the headboard. That is because hubby sleeps on the right side. Its been like this since day one and it would just be strange to change it. Even when the bed was against the wall and the left side was against the wall I still slept on the left side.
Since my wife and I have both been working crazy hours, I sleep on the side that’s unoccupied (I usually stay up late and she gets up early). This usually means the left side since she needs to be near the alarm clock, which is a change from our habit over the last decade where I usually slept on the right side.
Once things normalize, I suspect we’ll be going back to the old way as well.
OK. Headboard is against a wall. Right side of the bed (when facing headboard) is against another wall. I sleep on the left side, away from the wall. That’s because my radio and alarm is on the nighttable near the left side of the bed.
When I had a live-in girlfriend, I would always sleep on the inside of the bed, near the wall.
South side.
Wherever the wall is. I sleep on different sides if we’re on the bed or the futon (where the AC unit is) because the wall is on different sides. This is as much because I like the security of the wall as because he likes the open side.
Right side. Always has been, and without a thought as to why.
I know…because I’m always right!
Ask her, she’ll tell you, really.
As you face the headboard, I sleep on the left hand side of the bed. Passenger’s side (US perspective), if you view it from the “in use” position.
I only get about 4 inches on that side, as Mrs. Butler is a bedhog. 
I’d personally prefer to sleep on the other side, but the wife is a light sleeper, and laid claim on her side (and 3/4 of mine too) early on in our relationship. Like any good husband, I go where I’m told to go.
-Butler
I took the left side with my first wife, the right with my current wife.
Luckily, I’m sexually ambidextrous.
I end up on whatever side I feel comfortable sleeping on, which changes nightly.