I get this a lot from new students in my shotgun training sessions.  I focus on clays and wing shooting, but some of this transfers over to self defense loads and equipment.

Felt recoil has several deleterious effects.  It can cause bruising on the arm, shoulder and face.  It can result in physical anticipation of the shot, sometimes described as flinching.  It can also adversely alter gun mount and other body mechanics.  And it makes shooting a less than pleasant experience.  

The first thing to check is gun mount and overall fit.  The butt stock should rest squarely in the pocket where the deltoid and pectoral muscles come together.  The stock should be brought up to the face, not the neck contorted to bring the face down to the stock.  The pitch of the butt stock should be set so that the recoil is directed back into the shoulder, and not back and then up into the cheek.  There are other aspects to gun fit, stance and mount that I can address in a different post if interest for that detail exists.

Second, make sure that your shotgun stock is not too short for your shooting stance and style.  I see some students bring guns with very short LOPs, and they end up contorting their stance and mount to try and make the gun fit.  Those contortions cause all types of bad habits, and can result in bruising on the face and the resultant raising of the head from the stock in anticipation of recoil and/or a thumb knuckle in the eye.

Next, look at the type of shells that you are using.  If you are shooting a 12 gauge closed breach gun (pump, O/U, SxS, etc.), I suggest a 1 ounce load at 1150 fps or so for beginners.  That is a nicely patterning, soft shooting load that will decisively break clays without the associated pounding of a heavier shot charge out of a faster shell.  If you shoot an inertia or gas operated semi auto, you will have to try different loads to find the lightest recoiling one that will still consistently cycle the action.  I find that a 1 pounce load in the neighborhood of 1200 fps is usually a minimum for those types of guns.

Finally, make sure that you have a quality recoil pad.  Many factory pads are generic hard rubber, and provide very little protection.  I personally recommend a nice soft Kick-EEZ pad, appropriately fitted for length of pull.  Pachmayr Decelerator pads are also popular, but I prefer the energy dissipation of the Kick-EEZ.  Softer pads do wear out easier, though, so be aware of that.

It would be simpler to just buy a Benelli, but then OP couldn't post up a novel.  

It has been exactly a year since I shot my street howitzer.  Shot three rounds of trap on Saturday.  Thank you Benelli SBE-II.  

I had a student with a Benelli that didn't fit him.  As a result, he ended up with a bruised cheek and started lifting his head.  Then he came to me for the fix.

There are softer shooting shotguns than an inertia action Benelli, but not everyone wants or needs to buy a new gun when there are less expensive alternatives.

Any long gun not held tight to the shoulder will hurt. I explain to pull the shotgun in tight and keep it tight and that with a good recoil pad works wonders.

A liquid mercury stock insert helps too.  I have one in my side by each.  It is a hammer shotgun and I didn't want to put a recoil pad on it.

I added a Knoxx CompStock to a Mossburg 12ga for my son when he was 12 years old. Fairly small kid at the time and never fired a 12ga before. Had a 410 and was used to that recoil.

He went through a box of 25 shells without a peep. Afterwards asked him how his shoulder felt and he said it was fine.

I added one of those stocks to my Mossburg as well. The spring takes the initial jar out of the recoil. Especially with 3" OOB loads.

Added a limb saver recoil pad to my Benelli M1. It has a large factory muzzle brake on it, but that doesn't seem to do much if anything.

Good post. I just “souped” up my 870 and going to try some subsonic rounds.

Beretta shotguns are far superior to Benelli’s for clay shooting.  Especially when you get serious /  start competing.  I want to own a DT11 one day.

Also sold my fully upgraded Benelli m4 and bought a Beretta 1301 and couldn’t be happier.  The Benelli  m4 was stupid heavy.  I now own a 1301 Marine Tactical and 1301 Competition to go with my A400 and Silver Pigeon.

I also have 6 870’s, A Benny Hill Versamax, 2 1100’s, 3 Browning A5’s, a random S&W Pump, Mossberg 590 retrograde.  I fucking  love shotguns.

Inertia guns suck, give me a gas gun, I like my Remington 1100, people make a big deal out of cleaning gas guns or a stinkin "O" ring.

Benelli all the things!

M2 SBS by FredMan, on Flickr

For some smaller stature people...it helps to stymie recoil, but pushing out with the support hand and pulling in with the firing hand.

In order to see whether the recoil is pushing you back: Shoot rapid fire with a three or six shot string --- If the recoil is pushing you back...you are shooting in the wrong stance. Try using a fighters stance...standing more broadside to the target, with one foot somewhat rearward and weight on the balls of your feet.

To avoid hitting headphones while mounting the shotgun: Raise the shotgun somewhat forward of the shoulder pocket, and bring the buttstock straight back in; without dropping your head to the comb of the stock