The key here is to always remount on the second target.
When shooting pairs you will almost always find you have just enough time to remount the gun before shooting the second clay.
This is imperative and should be done when ever possible.
As soon as you have fired at the first clay, just slip the gun out of the shoulder a couple of inches for a split second, and then put it straight back into the cheek/shoulder and shoot the second clay.
The reason for doing this is because the recoil of the first shot can often put the gun slightly out of position in the shoulder each time the gun has been fired.
This is particularly so with larger loads where recoil is fierce (28g +).
It will make for a better second shot and may even improve on the first shot as it will generally improve your gun mount.
It should also be done when game shooting.