Just like a rifle, a shotgun intended for wing shooting needs to be set up to deliver projectiles where the sights are pointing. And I do mean sights, as in the plural version of the word. The front sight is obviously the bead at the end of the barrel, but most shooters don't realize the rear sight is their eye. Move either the bead or the eye in any direction and it will alter a shotgun's point of impact. As with iron sighted rifles, impact will shift in the same direction you move the rear sight and in the opposite direction of a front sight move.
A Shotgun Of A Different Kind:
You can start the process of sighting in a shotgun by shouldering an empty gun at home. Just pretend you're taking on a fast rising pheasant, but do it with your eyes closed. Shoulder the gun in a normal shooting position and then open your eyes and determine whether or not you can see the front bead. If you must reposition your head to see the bead, it's bad news and there may be some major work ahead. If you can see the bead, it's a good start; but it doesn't mean the gun is shooting where the bead is pointing; only actual shooting will reveal that.
At the range, put up a large piece of paper with three clearly visible aiming points—I use wrapping paper and blue painter's tape—and back off about ten paces. From this short distance you'll fire three shots using the tightest choke available and evaluate the results.
If you're lucky, the aiming points will become tattered holes and you can move off to the practice range and shoot aerial targets. If not, evaluate your paper target. If the shots are too high, you'll need to raise the front sight. Aftermarket sights like those made by TRUGLO that attach to shotgun ribs and feature fibre-optics are often higher than a conventional metal bead and are quick and easy to attach. A higher front bead will often lower your shot charge just enough to make a gun fit perfectly.
If you need to raise you point of impact, it's best to work at the butt end of the gun and raise the comb. One way is to use an aftermarket add-on pad like the Pac-Skin product made by Pachmayr®. This is a stick-on ambidextrous cheek pad, that looks just fine and can provide the little extra comb height needed.
Raising comb height a small amount is easily done with a stick-on cheek pad like the Pac-Skin.
Be warned, there's a lot more to completely fitting a shotgun than finding the right bead or comb height. However, this is a basic check that needs to be done by all wing shooters and corrected if a problem. In my experience, it's the one gun modification that can help your wing shooting more than anything else. If you want to go beyond this point, find an English gentleman with a tweed jacket and a briar pipe. He will build you a new stock and fit your shotgun like a custom glove. But then you won't have any excuses for missing.