I learned by listening to ducks off-season and conversing with them. Learn what they're saying and they'll answer back. And they do make the damnedest sounds compared to what's on the tapes.
Coming to waterfowl hunting comparatively late for this area at least, mostly I learned by hunting with a cousin that is super at calling ducks though he'll never win a fancy competition. Things like it's better to not call at all than call too much - everybody else I've hunted with calls way too much. And change if they're no responding well. One day they just would not come into our spread. Larry switched to a drake call using it very sparingly and we got ducks. He kept several calls on his lanyard all making different sounds, some cheap plastic and some fairly classy.
That's what decades of experience will do for you, I ain't got it though I do OK. Or I like to think I do OK anyway.
