Organs are as follows:
Head (aim at top of head)
Eye (aim for middle of head)
Lung (aim for left or right of chest)
Heart (aim straight in the middle of chest (breastbone area))
Liver (aim for middle left of torso)
Stomach (aim for middle right of torso)
Intestine (aim at lower torso)
Kidney (aim at lower torso)
Testicle (aim at genitals)
Once you successfully hit a body part, it will pop up on screen with "eye shot" or "liver shot" ect. Progress can be tracked in your game statistics. Good luck!