I have a 12 gage Mossberg 500. It’s very simple and very intuitive to operate.
A few IMHO tips:
If it’s for general usage (including self defense and hunting), do not buy a fancy, high-dollar shotgun. Get a *utility * shotgun, like a Mossberg 500 or Remington 870 w/ synthetic stock.
Read the owner’s manual. Thoroughly.
So, were you born with expert knowledge in the handling and service of small arms, or did aliens come an implant the training directly into your head at an early age?
I don’t think I can add anything to the previous answers of the questions posed by the o.p., but I would like to reinforce Tranquilis’ encouragement to obtain training. As previously mentioned, pump guns are prone to short-stroking, and are mechanically somewhat more complex to handle than you’d believe from use in the movies. Their length can also be awkward in an enclosed environment, so you need to take that into consideration for use and handling. Longarms are best used from a fixed position where you’re not going to be going around corners with the barrel sticking way out in front of you. It is not a “simple machine” in the mechanical sense, i.e. a lever or pulley, but is rather a fairly complex mechanism the operation of which can result in the projection of a mass of lead moving at lethal velocities, so training is definitely advisible, regardless if some “macho posturers come in and wank” about how you don’t need any training. With a shotgun, training doesn’t mean firing off hundreds of rounds–it’s not as if you’re practicing to be a long range marksman–but a moderate amount of live fire practice combined with suffiicent “cold” handling to make sure that you know how to handle, load, clear, and safe it in the dark, under stress, without hesitation. The last thing you want to happen when you hear what you think is someone breaking in is to struggle with or be unsure about your weapon; you should be devoting that attention to whether your suspicion is a credible threat and how you can deter them without being backed into a corner.
Regarding selection of shot placement, shooting someone in the legs is no guarantee that you won’t kill them; a shot that severs the femoral artery will be just as lethal as a shot to the heart or head, but not as effective. If you’re dropping the hammer on someone, you’ve elected to use lethal force in the eyes of the law, whether you’re pointing at the head or the knee, and you’d best be prepared to accept that responsiblity. In any case, when you are using a firearm for self-defense, there is no “shoot to wound” or “shoot to kill”; there is simply “shoot to hit”, and the most effective point of aim is the center of mass.
Oh, and I heartily endorse Crafter_Man’s recommendations.
Stranger
Get a Mossberg 500 with the riot barrel. 12 gauge, twin rails, a safety right under your thumb, and they have so much “play” in the system that you can fire one that has been buried in sand for a week. We actually did this one year. Not for a week, but for a day or so. Buried my Mossberg in sand, then dug it up, shook it to clear the barrel, jacked a round into the chamber and fired. No hu-hu.
But any weapon requires Carnegie Hall directions.
Agree. But it’s shoot to stop, not shoot to hit.
I’ll point out that often you can buy a double-barrled “coach” shotgun, with exposed hammers. Coud not be simplers- insert shells, pull back hammer, pull trigger. And, as far as intimidation goes, the dbl-bbl coach gun is about as scary as they get.
I think the problem lies with the gun salesman. Having been one, I know that some delight in deliberately confusing naifs, by spouting confusing and technical lingo.
Shoot to hit, and keep shooting until they stop. How about that?
But no shooting at someone’s legs, or shooting the gun out of their hand, or shooting through the hostage. Leave that to the Hollywood people.
Stranger
I’ll 3rd or 5th the aove suggestions as to a Mossberg 500. When I was growing up in Colorado you could get a small game license at age 12. The only thing I wanted for my 12th birthday was a shotgun.
At age 12, I not only was able to read and understand the operating instructions, I was able to totally disassemble the gun and put it back together without any instruction at all. (and to those who are horrified, this was carried out with adult supervision, but no adult input).
One bit of advice I would offer is to load one less than the full magazine capacity if you don’g shoot this gun regularly. Ideally you will never use the gun in a defensive situatation. If stored for many years with a full magazine, the magazine follower spring tends to relax enough that the last 1-3 rounds may not feed reliably.
A factor of a pump action shotgun not yet mentioned in this thread is the audio intimidation factor. Anyone who has ever heard the sound of an agitated rattlesnake, or a round being racked into a PA shotgun will never mistake the danger that sound represents. A home intruder hearing that sound may well shit himself in the urgency to abandon his evil intent.
One nice thing about a pump action shotgun for home defense; when you rack that puppy everyone knows exactly what it means.
Word. Another vote for the 870.
If you have a weapon for inside the home defense and have never shot it inside the home from the likely place you will be shooting from, you nor your family are anywhere ready for home defense IMO.
Get you a 5 gal. bucket 3/4 full of sand, cover with some heavy cloth held by a rubber cord or some such. Now, if you are going to be near the bed shotting towards the door, take that position, have the wife and kids lay in there beds and then sometime in the next hour, shoot three fast shots into the bucket.
If your SO still allows you to have a weapon in the house make them shoot off a few rounds in the house. then make sure everyone will and can do what they need to next while their ears are still in much pain and they are deaf.
If you have no idea what your 12 gage sounds like in the front hall and you have occasion to shot it there, you better have done it before or you will be over powewrd by the bad guys because you will be stupefied into inaction by the thunderous blast.
There is no substitute for practice in the actual conditions or as near they can be created.
YMMV – of course…
If you are going to keep a pump shotgun, you should be willing to keep it with shells in the magazine, IMHO. Loading it is complicated under stress, I wouldn’t want to do it. A Moss 500/600 is pretty much the same thing as a Winchester 570. A double is not more foolproof under stress, unless you are willing to keep rounds chambered. Also, doubles I use for hunting and target shooting are a lot more expensive. You can get a pump with a full riot package for $400, a double will start at a grand, and can be twice that easily.
This may well be illegal where many dudes live. IANAL. And, it would be safer to use blanks.
Home defense is always a personal issue. If you read the stats you have seconds and about 12 feet between you and the bad guy. So I would rather have a 45, with one in the chamber that that is ready to go with one flip of the safety.
They also make rounds with small BBs housed in a hollow “bullet.” I have many calibers but have never shot them to see the disbursement.
But I do have a semi-auto Benelli that is very light and a lot of fun “plinking.” Could never figure out why one would want a pump when a semi allows you to empty it with just a few pulls of the trigger.
Always remember, you can have more guns than you need but not all that you want.
I agree. I have a 12 gauge double barrel. I don’t think that guns as home defenders are all that good an idea but just the same, staring at the business end of a 12 gauge, double barrel will scare the most foolhardy interloper.
The problem with guns for defense is, if you pull a gun on someone you must be prepared to use it with no hesitation. And shoot to kill.
Frangible bullets; the most common is the Glaser Safety Slug. These have use in certain applications, but are poorly suited to home defense, as they tend to cause massive surface wounds but don’t penetrate more than a few inches. They also have a reputation for unreliable feeding in many automatics, and while it isn’t particularly an issue with home defense, are not accurate at longer ranges.
Stranger
That’s why my Glasers are loaded into a .44 Special revolver next to my desk. No feed problems, and enough power that even a 2" penetration will be enough to stop an antisocial deviant bent on mischief, especially since it will be followed by several more shots. 
(BTW, just as a data point, Glasers feed quite smoothly through my Firestar .40SW)
And, as a note, keeping a handgun under the pillow is pretty stupid as well - we’ve all woken up from a realistic dream, right?
Besides, handguns are tough to hit a target with under duress - there’s a reason most police shootings happen roughly within arm’s reach.
Stranger, I have seen these shells used on the ballistic gel tubes and saw a six to eight inch penetration and about a three inch spread. Is this inaccurate? Have I been misled?
To the OP, I keep a S&W 357 revolver at the ready in my home as well as a Glock 9mm. To me each has it’s special traits and I like them both. A 357 with hollow points is quite the effective home defence tool IMO. Plus, practice at the range is a lot of fun with both and inexpensive as you can use .38 rounds in the 357 to practice.
ETA: I keep the revolver loaded with Glasers and Hydro-shock type rounds staggered in the cylinder.
Note to self: when sent to assassinate silenus on Her Majesty’s instructions, unload the revolver first.silenus: [pointing a gun at Stranger] Shame. We’d barely got to know each other.
[pulls the trigger and realizes there are no bullets in it]
Stranger On A Train: [holds up a handful of Glaser Safety Slugs] I know where you keep your gun. I suppose that’s something.
Stranger