The answer for me depends on how long I am on the surface. If I'm just up for a few moments, there is not usually a reason for me to take it off so I just leave it in place. However if we've surfaced after a dive and are just floating around talking, I put it backwards around my forehead (lens in the back, mask strap in the front). I usually dive with my instructor (we're good friends) and am used to being drilled if I slip and just pull it up on my forehead without pulling it around so the mask strap is on my forehead. He says that when the mask strap is on the back of your head and you've just pulled the mask up away from your eyes, it's a sign of a diver in distress.