I was working with a green horse that often picked up the wrong lead after the fence. I just did a change after but I took a clinic with a trainer who said, if you're balanced to the fence and stay very very still through the fence the horse will land on the correct lead. Have to admit, I was kind of skeptical. I'm pretty still over the fence anyways but I took her advice and we worked on that during the days I rode with her. By the end of the week? Was landing on the correct lead almost every single time! It was a very miniscule change, but one that made a huge difference!