You can start by getting a harness and letting him get used to that, then attach lines to the harness and get him used to you walking behind him holding the lines. Teach him to move forward, stop, turn right and left. There is a great book, Travel at the Speed of Dog, you can get at
PWDpoocher@aol.com. Also if you google dog carting you will come up with lots of sites that can help you get started. Are you doing obedience training with your dog? If you have a dog who is already in training it makes it much easier.