The protections afforded by the Castle Doctrine and Stand Your Ground laws are significant in providing legal rights to those who discharge firearms in protection of themselves. It does not give a homeowner the right to shoot people that come upon their property.
The Castle Doctrine does not require a home owner to retreat before using deadly force to protect himself or his family. The homeowner can assume that an invader has bad intentions and his safety is in jeopardy. Stand Your Ground laws similarly protect those who are in imminent danger and do not require retreat when they reasonably believe it to be necessary to defend against certain violent crimes.
This does not mean you get to shoot neighbors, visitors, solicitors, or people who turn into the wrong driveway. If you are in fear of your life, it must be a reasonable fear. For example, if you fear someone because of the color of their skin, that is not reasonable. If you fear someone who drove up your driveway, that is not reasonable. If you fear someone that rings your doorbell, that is not reasonable.
Of course there are fact scenarios where you may use deadly force against a person ringing the doorbell and deadly force may be reasonable. Put an assault rifle in his hands… have him screaming I’m going to kill someone… have him firing shots into the house. That is very different than someone ringing the door to discuss buying magazines or contributing to their basketball team.
In short, think before acting. If someone breaks into your house, call 911 and protect yourself. Do not shoot the neighbor because his kid’s ball came into your yard.