Supplies being dropped off of plane
MultiFazed: The “head on” face shots are actually shot at a slight angle. So the actor is looking at the camera in the mirror, and not at themselves.
And in cases where it’s absolutely impossible to shoot the mirror at an angle, they just edit out the camera using computer software in post-production.
Yerunkle: Usually with rotoscoping, that is painting the camera and crew out of each frame with tools like photoshop.
Shooting at an angle is another good one. James Cameron in T2 used a window and a ‘mirrored’ duplicate set. Sucker punch used body doubles.
internerd91: Sometimes it’s not actually a mirror but an opening into another room and they use doubles to compose the shot. They did this in Terminator 2 before computer trickery was good enough using Linda Hamilton’s twin sister.
TheLaVeyan: They dress the camera up like the actor, throw a tie on it, and hope that you don’t notice.
Arokthis: One easy way to test this for yourself is to get a medium-sized mirror (bathroom medicine cabinet size) and a friend.
Hold the mirror up (or put it on a wall) at arm’s length. Have your friend stand where they can see the back of your head and your face in the mirror at the same time. Odds are they won’t be able to see themselves in the mirror.