Hi. I have been training Welsh ponies and Haflingers to drive for over 30 years. One thing is for sure, I know what I know from experience! Believe me, I've been in enough wrecks that I have devised ways to avoid the things that cause them! I would be glad to share my knowledge with anyone who wants to learn, as I probably won't be needing it too much longer,(Ha! I'm just refering to the fact that I am getting so much older and wiser) and I sure enjoy talking about such things. But there is no short answer to this question. It takes a lot of practice and patience, as do a lot of things in life. But the work is also the fun, I have always thought, anyway. Write back if you wish to hear step one. And by the way, ground driving as you mentioned is a great place to start(no harness necessary).