I know I keep mentioning this, but it is SO IMPORTANT for you to understand that in the dog potty training process, there are going to be accidents. What you do when your dog has an accident is very important. Yes I know that nobody likes cleaning up after the fact but if you react negatively your dog will start to associate your anger or frustration with him going to the bathroom and will be afraid to eliminate around you. I would say this is the biggest mistake people make while dog potty training.
A training class is not there to train your dog. Its purpose is to teach you to train your dog so you will need to be committed to train your dog for short sessions (5 minutes) several times a day rather than just simply turn up for classes! This little bit of training everyday will be repaid with a lifetime of living with a well behaved dog. You will also learn to avoid problems before they begin as well as receive help to overcome any that you already have with your dog.