• FIRST: You must have a reasonable belief that your’e being attacked or about to be attacked. 
• SECOND: Unless you are in your home, you must try to retreat (i.e., run away) before you can defend yourself.  In other words, you need to try to retreat or run away or get away in any way you can, until you can’t. But you don’t have to retreat from your own home before defending yourself.
• THIRD: You can only defend yourself from the attack with a similar or proportional amount of force. 

If you’re attacked with non-deadly force (i.e. fist and feet, etc.) you can’t respond by pulling out a gun and shooting them. Non-deadly attacks mean you can only use a Non-deadly defense. 

If you’re attacked with deadly force (knife, gun, bat, etc.) where you could have great bodily harm or death from the attack, you can respond in kind. Although you can use deadly force, it must be limited to only the amount of force needed to repel the attack.