Plenty of good suggestions here, the ones I'd second are taking a self-defense/gun handling course, and shooting as many different guns as you can. If you take a course, you'll have a chance to ask specific questions, hear the questions others ask (that you might not have thought of) and get different viewpoints on lots of related issues. Another suggestion is to get a copy of Massad Ayoob"s book, "In The Gravest Extreme", which will tune you into ALL aspects of armed self defense, in a myriad of situations. He covers the mental, physical, psychological, and legal aspects thoroughly, and I ask that my own Beginning Handgun students read it. I was a PD rangemaster, and there were several points in the book that I'd either forgotten about, or had never even thought of. Required Reading!
As for weapons choice, if anyone else in the house may have to learn/use it, I'd recommend a double action revolver, simple is good in high-stress situations. It's also mechanically simpler, and doesn't have those things on the sides that all look alike and stick out funny. Not many people find the need to reload in a home defense scenario, so that's less of a concern. (Speedloaders are STILL a good idea, however!) But if the other people around you are relatively skilled and clearheaded, an auto can be a good choice as well. Good training is important, because in stressful situations, the brain tends to freeze, and you follow whatever training you have.
Whatever you do, don't buy a gun, shoot a box of ammo thru it, and throw it in a drawer, good pistol skills require CONSTANT practice. I'm over fifty, have been shooting for three decades, and if I don't get to the range on a regular basis, I get rusty as a barn door. My 15-year old son just smoked me on bowling pins last week, and not just once, I was shooting a gun I rarely practice with. It DOES make a huge difference.
I don't often say this, but some folks have good heads and motor skills and live in condition yellow all the time. Others have no business around guns. Most are somewhere in between. My point is, if you're not sure, ask, and if the answer doesn't sound right, keep asking until you get the feedback you're looking for. There are a lot of gray areas, and as soon as you get one question answered, another question will come to you. Listen, learn, and practice! It's not rocket science, but doing it wrong can get you or someone else killed. Hope this helps.
Papajohn