When nobody's home, I just kinda do whatever. Sometimes I close it, sometimes I leave it wide open, sometimes I close it most of the way and just leave a little crack open.
When there are people home, I close the shit out of it. Though, when I was A LOT younger (we're talking about six years old) I used to leave the door completely open regardless of whether or not there were people around. Then one day my mom walked by with some random person and I very quickly learned why most people close the door.
Common sense isn't one of my strong points.