Back when I used to shoot just 1 deer a year, I used to slice the deer liver and fry it just like beef liver with bacon and onion. (be sure to remove the bile sac off without puncturing it). However when I started shooting 2, 3, 4 or more deer a year, the liver started accumelating in the bottom of the freezer so I seldom keep it anymore.
For the heart, it is good fried too but I always just grind it up and make more sausage out of it.
IaCraig