How I look at the "except when to do so would injure them or others" is if someone is really mad at you for something you did, it is good for you to look at that situation and see where what you did or said was wrong or inappropriate and then maybe the BEST way to handle that is to leave that person alone. To go to them to apologize would only make matters worse. Stir the pot so to speak.
Sometimes our making amends doesn't necessarily mean we even have to go to those people, places or things and directly "fixing" our wrong doing(s) but rather walking a better and spiritual path so those people, places or things see that we have "cleaned up our act."
As the others have said, working the steps thoroughly are best. I feel like steps 4-9 really go hand in hand and as you go through the process you'll find that you may even have to make amends to yourself. That changing what we do is even something so simple as reacting to things differently or realizing that we played a part in it and knowing NOT to repeat our actions.
Hope that helps a little.
