I think most people who educate themselves about SD / HD do some basic things like identify the choke points in their house and points of entry / egress.
I am fortunate in the layout of my condo in that my kid's bedroom is further down the hall than my bedroom - so, my door opens on the hall which is the choke point for my home.
In addition to identifying chokepoints, I think most people think about cover.
I basically have no cover in my home, except the minimal cover provided by 2x4s of a door frame.
I had German Sheperds my whole life and I found them to be really intelligent, courageous dogs with natural gaurd instincts. One of my German Sheperds actually patrolled our house several times a night, looked into every bedroom, looked out every window, and then would lay down at at the top of the stairs - the point where all bedrooms and family members could best be gaurded. Unfotunately I have a daughter who is allergic to dogs so the gaurd dog option is out while we look for a dog she's not allergic too. And she's already proven to be allergic to some supposedly hypo-allergenic breeds.
My feeling is that if I am upstairs and intruders are downstairs I can shout "Get out of here - I'm armed, I'm calling the police !" And they would probably flee. And I could be ready to defend the hallway until the police arrived.
But if I don't wake up until they are in my upstairs hallway... my feeling is that shouting or yelling "freeze" or something like that is just going to get me shot.
Unfortunately, we live in a litagaous society where a good portion of jurors have no idea about the reality of the dynamics of shootouts and have many misconceptions fostered by Hollywood's ridiculous portrayals. And there are lawyers who know how to expertly exploit those misconceptions.
I think that's why a solid Castle Doctrine with no burden to retreat is so so important.