A deer's front shoulder covers about 1/2 of the heart and when selecting where to shoot, I aim for the 2:00 position of the front leg - placing the crosshairs straight up the rear portion of the front leg and squeezing the trigger when they are about 1" below the top of the shoulder.
Aim for the heart. If you're a little off, you still hit the lungs, anyway. Also, if the deer jumps the string, better chance of a hit if you aim for the heart. (imo)
Dave has a excellent point, however, I always aim for lungs but aim low in case the deer ducks at the release, actually they jump but they will be crouching when the arrow arrives unless its a long shot or they catch movement of your draw.
Accuracy. What an incredible way to give yourself a true advantage.
Go to your club and get a bunch of guys together - and put a target out there at 250 meters. Break out the deer rifles and see who can shoot a decent group, even off of the bench, at this distance. I think you will be shocked at how few can do it.
So - with that in mind, I recently set out to try to develop a semi-custom rifle that I could afford and that would shoot - repeatedly - at MOA.
I started with a platform that I love...