Concealed Nation put up a concise article with 10 key points of what a concealed carrier should not do. http://concealednation.org/2015/07/10-things-you-should-never-do-as-a-concealed-carrier/
Adding an additional point of discussion. You vs A Third Party Conflict
Be careful when getting involve in a third-party incident, it can be a double edge sword. You want to be the Good Samaritan or the hero by trying help that person who you think is being beaten furiously. If you’re going to get involve, you better be absolutely sure on what is going on. Here are some examples when to get involve and when not to.
When not to
You just walked out of a 7-Eleven and you see an older man in his early 60’s beating a younger guy in the face on the ground against the pavement. You just ran in to this action, but do you know how it started? Or who is the victim here? Presumably you want to draw your pistol to shoot the older guy. Take a step back. Let’s say while you were waiting in line to check-out, the older guy in the parking lot was getting out of his car and this young thug came up to him with a hammer in attempt to rob the older guy as he was exiting his vehicle. Then somehow the older guy was able to get the upper hand in defending himself, which he turned the tables around. Obviously the older guy didn’t have a gun or any other force multiplier (besides his fist and hand-to-hand skills) while the younger guy was using lethal force with his weapon (the hammer). As soon as you came out of those doors, you didn’t see how it all went down, but all you saw was the older guy beating on the young guy on the ground.
Second Example. You came out of Walmart and see a man and a woman in some kind of physical altercation. The man is tying the women’s hands together, wrestling her down to the ground and trying to restrain her, plus you see a knife on the floor next to them. You might want to pull your gun out and hold the man at gun point, or fire a warning shot (that’s a NO-NO, see the article in the link above), or shoot to stop what you think is the threat. But you didn’t know that the woman (his crazy ex-girlfriend jacked up on something) hand the knife in her hand who was trying to attack him. Know before you get involve. Remember, you’re not the police. Your responsibly is to protect yourself and your love ones who are with you.
When to be the Good Samaritan
You’re standing next to your car pumping gas and this lady pulls up to the adjacent gas pump and she is alone. She gets out the car, swipes the credit card, starts to pump gas and after about 20 seconds a guy comes out from some corner. Next thing you see a struggle and he is trying to take her purse, then he pulls out a knife and starts to ice pick her. If no one intervenes in a heartbeat, she can be gravely injured and possibly die to her injures. In this case it will be ok to pull your carry gun and fire at this guy to stop him from doing any more harm to her.
Another good example where you can intervene such as a terrorist gunman shooting at random people at a mall if you’re really close to him. As you hide, and knowing if you try to make a run from your cover spot, he might see and try to shoot you. If you have that vantage point, take that shot. Now remember if he is down (assuming just a lone wolf), just make sure the scene is safe and holster that weapon. You don’t want police running at you and see a gun in your hand.
If you are away from the gun fire, get the hell out! Some time indoors it can be hard to tell where the shot are coming from. Observe and move out accordingly.
Make sure to know your state laws too.