As others have said, a lot depends on the course you shoot. One place I shoot at has two courses, a recreational course and a tournament course. Most courses have at least a couple of presentations that are very, very difficult.
As far as what you "should" be hitting... I have a friend who goes with me occasionally, probably half a dozen times a year. He'll generally hit around 35%. I usually shoot about 85% on the average recreational course. I've been doing it for years, last few years only average probably once a month.
I don't get too technical. If you ask me what choke tube(s) I have in my gun I wouldn't be able to tell you (unless I'm using my bird gun with fixed chokes in which case it's 1/2 and VZ. I also don't get real worked up about what ammo I'm using. I just take all the shots presented with whatever choke and ammo I'm using.
When I started shooting this stuff back in the '90's, everybody started with their trigger-finger hand below their belt. Now I see a lot of people shooting with a mounted gun, like trap or skeet. I don't do that (unless I'm shooting trap or skeet.)
One thing for sure, shoot sporting clays regularly and it will make you a better shot on birds for sure.
