1. Shooting a poor-fitting gun
Becoming a good shot starts with having a shotgun that fits. If your gun doesn't fit your physical characteristics, you'll never be a proficient wing shot. Surprisingly, however, many shooters give little consideration to proper fit when purchasing a fowling piece. As a result, the guns they use cause many of their problems.
The shotgun you buy should feel comfortable, mount easily to your shoulder and point like an extension of your arm. As writer Wade Bourne once put it, "...a shotgun should be like a good dance partner that flows smoothly with your lead."
To check the shotgun you have, grab it out of your gun cabinet, be sure it's unloaded and pick an imaginary target like a ceiling light or picture on the wall. Now snap off a quick imaginary shot — both eyes open, no aiming. Now close one eye and look down the barrel. If you're reasonably on target, your gun fits close enough. If you see the entire barrel, or none of it, your fit is out of whack. If you have to move your head in order to line your eyesight down the barrel, your stock is too long or too short.
If necessary, you can hire a gunsmith to custom fit a shotgun to your exact measurements at minimal expense. But be sure to check your new gun's fit when wearing hunting clothes, including a parka.
2. Failing to focus
To bag a duck, you must focus on that duck and that duck alone. Yet many hunters fail to do this. When a flock comes close, it's tempting to aim into the mass and fire randomly instead of choosing a single target. But such an effort usually results in embarrassing misses.
When you see several birds approaching, choose a single, and concentrate on proper aim and follow-through. Don't think about trying for a double. If you miss a shot, adjust, but stay with the same bird. Don't attempt to bag a different duck. Get one on the water before thinking about a second.
Here's another helpful hint: load only one shotshell at a time until your shooting improves. Knowing you have only one chance each time improves your concentration and can help you become a better shot.