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.
Practice sitting, kneeling, resting your rifle against a tree, and other real-life situations. You won't have a nice bench-rest out there in the field.
Make your first shot your best shot. If you miss clean, you may want to refrain from shooting again, until you have a better rest or have reduced the distance between you and your target.
Set a good example for others. When around kids and adults new to hunting, behave in a way that reflects well upon yourself and all hunters.
Consider ripping up your deer or elk tag if you can't recover a wounded animal. Your tag is intended for one animal.
Consider that others may not enjoy seeing a bloody carcass hanging across your hood or tailgate.
More to come...
"We are what we repeatedly do. Excellence, then, is not an act, but a habit." —Aristotle
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.
Shoot unless you feel good about the shot.Remember that there will always be another day. Don't wound an animal just because you couldn't control your enthusiasm.
Let your desire to take an animal overwhelm your duty to hunt right.
Let other hunters negatively influence your behavior. Make the right choices and decisions regardless of what everyone else is doing.
Teach others the wrong things. Be a paragon of responsibility and honor in the field, and set a good example.
Boast about your kill-shot or detail the animal's death throes. Regale your friends and family with descriptions of the chase, not the bloodshed.
Drive down Main Street in Bozeman with a bloody elk hanging off your flatbed. (Downtown Gardiner, maybe.)
More to come...
Ethics may be subjective, but there are some types of behavior to embrace, and some to eschew. Here's a list that reflects many of the experience and values of most ethical hunters. (Remember that these are guidelines, not hard-fast rules.)