Verify whether your shot hit an animal or not. Inspect for blood or other signs of wounded game. Follow the trail until you're absolutely sure.
Know your limits and avoid exceeding them. If you only practice to 200 yards at the range, don't shoot beyond that in the field.
"A peculiar virtue in wildlife ethics is that the hunter ordinarily has no gallery to applaud or disapprove of his conduct. Whatever his acts, they are dictated by his own conscience, rather than by a mob of onlookers. It is difficult to exaggerate the importance of this fact." —Aldo Leopold, A Sand County Almanac
Leave a wounded animal. Do everything you can, including putting a bird dog on the scent, before giving up.
Shoot into a herd or at running animals. Odds are you'll wound the game, subjecting it to a slow and painful death.
Ethics, unlike laws, are specific to each individual. Every hunter must develop his own set of rules for honorable behavior while afield. However, like honor, a basic code of conduct exists. The following tenets should be followed at all times: