Ideally if it was possible you would want your open choke barrel to shoot very high, since your first shot is a fast rising bird. Since the second shot is usually flattening out or thinking about dropping (unless you are a real fast shooter) you would want your tightly choked barrel to shoot right on. (approx)
With adjustable ribs and different size barrel hangers between some barrels, some people can accomplish that!
Set the gun up so the second shot is as flat as possible (50/50). Shoot a light load for the first shot so you stay in the gun for the second shot. You will probably have to cover the first bird inorder to hit it.
It would be best if the first barrel shot high and the second barrel shot flat. Check it at the patterning board at 13yds from a rest and see if you are lucky and have one that is set up like that. HMB
I hold my gun under and slightly outside of where I want to break the first target....I do not spot shoot it. I track it, shoot it and swing for the second target. Made me much smoother from start to finish on each pair, regardless of which post I'm on. When asked for advice, I've always adivsed that you practice shooting first targets only until you can shoot them comfortably fast. Then start shooting pairs. This was how Britt Robinson refined my technique at his clinic. That and shooting lots of practice. It's all about timing and consistency.