There have been recent threads on chokes, shotguns, and shells and in each the posters often relate the subject under discussion to accuracy and/or killing power. None of these three things are, in my view, the primary factor in the ratio of shots fired to birds down. Shooting is a hand/eye coordination sport and we need to look at the factors affecting that performance to understand why some shoot better than others and why our own accuracy varies from day to day and season to season. Only then can we improve or help others improve. Ian F. in one of those threads mentioned recoil as a factor affecting accuracy and I assume he was referring to involuntary flinching so that could tie the kind of gun directly to accuracy of aim.
In my case the single biggest reason I miss is gun alignment ( followed closely, with brant and Canadas, and sometimes ducks, by sitting up too soon). This holds true now ( I probably average 1.5 to 2 shots per bird down on ducks, better on snows) to back when I rarely hit anything (a box and a half for 4 ducks was a good day). If when you bring the gun to shoulder you don't automatically, every time, have the gun tucked under your cheek so that the bead sits on the back of the barrel you will almost surely miss. I now surprisingly frequently hit shots where I know the gun wasn't in the right alignment, but it's taken the upstairs computer 40 years to get to that stage. A lot of things affect achieving this alignment---eg. thickness of clothing worn, body position relative to where the bird is coming from, how far to the right or left you have to swing to get on and past the bird, fit of the gun to you, whether you start sitting or standing, etc. (there are , I am sure, lots of others). For instance when hunting brant with the extra Helly on over my marsh hunt jacket I have to make sure I throw the gun out further before I bring it to my shoulder or it will hang up and be too low in my shoulder to get the correct sight plane and I will be "seeing barrel". I still regularly practice bringing the gun to shoulder at home so that it ends up pointed at a chosen spot on the wall or ceiling with the sight plane bead-on-barrel (if you can see any part of the barrel you’re out of whack).
Another factor to be aware of when learning to shoot birds is, when you go out to hunt make sure you don't have all your focus on the bird when you sit up to shoot. I finally started to hit birds (with a friend's help) by repeating to myself "Gun first...gun first...gun first" as the birds were incoming so that when I sat up to shoot, before I looked at the bird , I checked the barrel/bead alignment. If good then swing on the bird, if not, fix it then go to the bird. After doing this enough it will come naturally and you can dispense with the "gun first" prayer, but when my shooting goes off it's what I always go back to first.
Another big cause, I think, of missing decoying birds is sitting up way too soon . I do this a lot on Canada geese (but often on the other birds too) and it means I end up with too long a shot by the time I get on the bird and past him and pull the trigger. Canadas are so big and look so close as they are setting into the decoys that I think I feel like I'm cheating if I let them come right in.
Another easy way to set yourself up to miss is to position yourself too far from your decoys. If you are 35 yds. away then, by the time you sit up, get on and past the bird, and pull the trigger you could well be trying a 50+yd. shot, and believe me, that is a much tougher shot for a learner to make than a 25 yd. shot. This factor is especially important when the wind's blowing hard because the birds can flare away with the wind (often in a curving flight line that will also throw off your lead) and gain a lot of ground on you before you shoot. Perfect your hide and set up close.
These are just a few ideas meant to help out those who are new to the game and struggling with "missing". Even when you get the above concepts under control there is still a lot of practice needed ( on real birds, in real hunt situations----while clays have their place in the whole process I believe one can only become a good bird shooter by shooting at lots of birds) before your brain will build in the correct lead for distance, wind, angle of the bird's flight, etc.
What other advice can we come up with here to improve accuracy?