Proper form. Gun up. Head down and keep it down. That's what I screw up most often. If I get in a hurry or after the first shot I pick my head up to find the next bird.
Also don't just focus on one bird, but where on that bird you want to hit him. If you are aware that there are any other birds in the world, you will miss almost every time.
If there are a bunch of birds, pick out your bird before you come up to shoot and stay focused on it. I pick mine as soon as I can. Just focus on that one as if it is the only bird. If they do something that forces you to switch, pick a new bird and focus on that one. And that should be the only bird you shoot at if you miss all three shots.
I missed a pair yesterday, beside being too far and I should not have shot
I jumped to the next bird right after I missed the first, which is probably why I missed the first. Then I jumped back to the first after I missed the second. I probably even picked my head up. Did just about everything wrong I could on the first shots of the year. At least I got to redeem myself on three singles and looked like I knew what I was doing after that.