Just my $.02 worth.
I am 66 and when I was 16-17 I worked at Roberts' Shooting Park in Elkhorn NE, pulling/setting trap and skeet for 2 years ('68-'70). I don't pretend to be a coach but I learned many things from the older shooters that helped me immensely for clays, pheasant, quail, and grouse.
Don't stop moving the gun. That is the one thing that causes the gunner to shoot behind or lower than the bird. I learned, as a skeet puller, to stand directly behind the shooter, watch the barrel swing, and see the shot "cloud" when the trigger was pulled, and then suggest not to stop moving the gun. Most did not believe they were stopping the gun.
Gun fit is very important. My 870 12 gauge VR IC choke 26" barrel had a very minimal drop at the heel which allowed me to see the entire top of the rib with an entire cheek weld. That was very important to me at skeet and also at live game birds. A lot of guns have an excessive drop at the heel that will not allow full view of the bird, causing the shooter to "blot" out the bird when pulling the trigger. That is not an optimum situation.
I was on leave from the USAF in the fall of 1972 at home in Omaha and my Dad invited me to a pheasant hunt the next day around David City NE, which I gladly accepted. My 870 was in USAF lockup in Kansas so he offered me to use his Win Model 12 16 gauge FC which had a very good aftermarket stock. I took the only 2 pheasants that day, and one was paced out at 65. I am not bragging, but just keep the gun moving!
This will do more for your shooting scores than anything else.
Jim