I would also recommend the Doris Ganton book as being very informative and having good photos of what is being explained in the learning steps. It is always the first book I recommend to beginners. If you can locate the video as well, it is also helpful. Some folks like video over reading a book to understand things better.
The main thing with Driving training is to make sure the animal is totally understanding and obedient at each step of training. They MUST respond immediately, CORRECTLY, to commands given. As the Trainer, you need to ask and GET the correct response the FIRST time. If you ask and ask and ASK with wrong response or no response, you are training horse to be bad!!
Your WHOA command has to be instant, and pretty much a loose rein, because that is your emergency brake. If something happens, horse must be stopped, the WHOA word will help you bunches! Second in importance is Stand training. I actually time these with a watch, so we get standing still longer and longer times. I have a Stand started in the ground work, then when we get hitched. Driving animals usually spend quite a bit of time standing about, so they need to be GOOD at it. They stand for hitching, then with vehicle attached, they stand you to get in or out. They stand while you talk to folks on your driving routes, waiting for classes, waiting for others to get stuff around. Stand is about the BEST GAIT on a Driving horse!! Often practicing the Stand when horse is a bit tired makes it easier for him, and maybe facing a wall at the beginning. Stand practice should be done in various places, so he will Stand wherever you ask him to as he gains experience.
Get a whip, learn how to use it as the tool it is meant to be. You have no legs in Driving, so whip touches on sides, shoulder, work like a rider's legs would. Light flick is all the touch most animals need as they understand what you are asking. No rump whacking, rein slapping on the rump top, tends to make them kicky behind! TV horses are NOT good examples of what you do driving most animals.
Do your ground training until horse is bored and obedient, accepting of things you ask. Then you hitch and repeat all those things again to the bored stages. You don't want horse surprised or worried. A kicking strap over the hips is recommended these days for beginner horses just hitched. It can PREVENT some problems from ever happening.
Stay safe, make training enjoyable for the horse and we will be waiting to hear about your progress.