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.
One of the most important pieces of equipment that you will take hunting is a good quality pair of optics and they take some care to give you the performance that you want. So here are a few tips.
Use some alcohol and cheese cloth to clean the lenses. I will usually pick up an extra cleaning kit from my optician when I have my eyes examined.
Don't touch the lens with your fingers. If there is a stick or a bug on them blow it off.
Use the lens covers. They are there...