I always aim for the heart. That way, if they duck, I still get the lungs.and if they don't then I got a nice heart shot.
This is good advice. Some deer duck at the shot and some don't. I am not an advocate of aiming so low that if the deerjust stands there you miss the vitals. Put your pin on their heart and it will be a rare case where a deer ducks under that. I haven't had a deer limbo under one of my arrows in many years.