IMO- its tough to train a dog this old because they have already been taught..thats its ok to jump on people, chew whatever they want,not listen..whatever.But allowing certain behaviors the dog has been trained that they are ok and acceptable. Not his fault but thats what you have. It can be done but you need to be firm at every step and it can take a while. You can enroll him in a class and get some good training books-Richard Wolters has written many. They are all good but try for the Family Dog ( ebay or amazon) Hope this helps.
It's never too late to start training, and at 15 months he's still a puppy. Consistency and patience are very important. Look for a local Obedience, Training, or Kennel club, and they can help you choose the right type of class.
its not that its too late..its just it going to take longer and a tougher process on both you and the dog. You are going to be RE-training him..not just training. Classes are a good idea and the trainer will more experience dealing with this so you aren't going it alone.
it is never too late, I have trained dogs with absolutely no training that were well over 2 years of age. welcome to the board.
Start callling around and asking other pet owners who they recommend. Stay away from trainers that use brute force or those that insist that there is ONE way to train ALL dogs. Each dog is different. Also note that training classes train YOU, the human, how to train the dog (dogs don't need help, owners need to learn how to train). A class is a great first step, remember to practice every day though.
I do agree with the above, you will have to be consistent for longer as the dog will likely rebuke the new rules. But hang in there, it is very do-able.
What are the key issues? What is your pups daily routine?