First thing is to KNOW the laws of your state. Some are insane.
In Texas you can use deadly force over something as trivial as someone running away with your $400 TV. Yea, they are a scumbag, but larceny is not a capital offense. A TV ain't worth the hassle, and that's why we have insurance.
In NC deadly force can be used if you believe deadly force is necessary to prevent an imminent threat of death, great bodily harm, or sexual assault. The use of deadly force cannot be used to protect property.