I had a K9 unit and these are the most important things I learned at doggie school from one of the best:
Be consistent and clear. He will be confused otherwise.
Be firm, but not mean, when he messes up and award/praise/love on him for good behavior.
Bond with your dog. He/she is sensitive and will usually want to please you.
Some pet stores like PetSmart have obedience classes you can attend with your dog and there is a lot if information on the internet if you have specific things in mind.