1) Avoid danger. Stay away from bad places and situations where violence may occur. Do not go looking for trouble. Do not associate with people who generate trouble.
2) Mitigate trouble. Attempt to prevent a bad situation from escalating. Given verbal aggression, even if you are in the right, sometimes simply apologizing is enough to calm down an aggressor. If you are confronted by thugs, do your best to keep calm and attempt to leave. Always call the police if a situation sours, assuming you have the time. The call will not save you, but it makes a clear record of who is the victim and who is the aggressor. Simply being armed will often end a bad situation before it turns dire, but it is unwise to give away your tactical advantage before the actual need arises.
3) Pay attention. Do not take another's actions or intentions for granted. Do not underestimate anyone. Always maintain situational awareness. Know your escape routes. Know your assets and liabilities. Keep a dynamic plan in your mind to handle your current situation. Think ahead. Never assume you are safe, because bad things happen to good people everywhere, not just in dark alleys.
4) Be prepared. Always have the necessary tools to defend yourself. That doesn't just mean having a gun, it means being well trained. Know how to draw your weapon, know how to aim and fire your weapon, and practice often. Be prepared to use your weapon if need be.
5) Fight to live. In deadly combat, there is no such thing as a fair fight. If your life, or a life you are defending is put in jeopardy, show no mercy until the threat has been eliminated. Any method of preserving innocent life, at this point is legitimate.
6) Remain calm. At least, as calm as possible... There will be plenty of time to panic once you are safe. Remember rule 3. Act in a reasonable manner. This is probably the hardest rule to follow, given the escalated emotional state you will be in when the time comes to exercise your right to self defense. In most of the country, you are allowed to match your defensive force to the magnitude of the aggressive force. There are situations where it is fair to assume your life is at risk, and others where it is not. When there is doubt, it is still "better to be tried by 12 than carried by 6."