I try and learn from my mistakes, and not repeat them. I've done some misguided and stupid things in the woods, I learn from those errors and do not repeat them (often :-D ). Not doing stupid things often leads me to being a better, more ethical hunter.
Another thing I don't do is describe my hunts in grisly, bloody detail to people who are sensitive to such things. I know a few guys who like to shock and disgust the non hunters by describing how a deer went down, whether it was quick or slow, how much blood was spilled, showing bloody pictures of a hunt, etc. These tales do not do us hunters any favors, they paint us with a wide brush as cruel, bloodthirsty savages. An ethical hunter is not cruel, nor bloodthirsty. By respecting the sensitiviites of non hunters, even anti hunters, I like to think that I bring credibility and respect to other hunters, myself included. Am I pulling a few punches? Sure I am.
One other thing I hear a lot is "I'm going out to kill something!" NO NO NO. Again, painting us as bloodthirsty killers. I hunt to get outdoors, to enjoy time alone and with others, to observe animals, and to put meat on the table. I am not out there to kill for the sake of killing. Any hunter who allows others to think that he is out there simply to kill is not doing his sport any favors.
How do I practice ethics? I try and show myself and other hunters in as positive a light as possible, I don't try and shock or offend non hunters, and I try to cleanly kill and process all game that I take.