No matter where you aim to hit, It always helps to have the quitest bow possible, In all reality Where you aim all depends on the deer, and what I mean is, if the deer is nice and calm and casualy just lumbering along and not on high aleart the chances of him JUMPING the string decrese quite a bit, now if the deer seems a bit edgey and does not looked relaxed then you have a better chance of him jumping the string,, I like to to aim for the Heart that way I still have a better chance of hitting the lungs if the deer pulls under, I think it's best to aim where you will feel more confident and have the best chance of hitting the mark. There is a lot of good advice in here it's up to you to use it what ever way is best for you....