Alright, so there's a back story to this post. We recently (maybe a month ago) acquired a foster horse at one of the five barns I manage. My trainer/BO accepted her with the agreement that she would mainly be a project for me. She is a three year old Thoroughbred mare named Shadow, and she couldn't be more awesome. She is kind and willing, and I don't believe she possesses a mean bone in her body. Today, I had her out on the trails, and except for a relatively minor spook, she was exceptional. Calm and focused, wtc without any rushing or disobedience. Later, while I was feeding, my trainer came to help me with my car, and I mentioned to her how well-behaved Shadow was on the trail. I told her that I couldn't believe a three year old Thoroughbred mare was so much better behaved and easier to handle out on the trails than my 16 year old Quarter Horse gelding. Her response was that Shadow doesn't have any bad training to undo.
So this got me thinking, how do you "undo" bad training. I've been working on the trail problems with my man for a few months now, and he's gotten better, but still has the tendency to want to take off, and will throw a fit the rest of the ride if you don't let him (sometimes even if you do). I've been collecting and leg yielding and such to distract him from his desire to run, and it's been slowly successful. But my question is, what is YOUR method to fix poor training in the past? How do you handle such a situation?