I grew up on a dairy farm. We had a cow dog that was a Border Collie. Teddy was his name and was about 6 years old when I started to hunt ducks. I taught teddy to retrieve ducks. My Dad was a horse trainer and he told me that to train an animal you have to be smarter than the animal. Don't hit the animal, don't yell or threaten them. When they do what you ask reward them with a treat or praising and petting/rubbing. In the summer I would shoot coots in the lake and used those to train him. Following my dads advice and methods he took the job of retrieving ducks just as good as he did in herding cows.
Over the years I've always had a dog, when I went away to school,the first few months that is what I was most homesick for was my dog. I have owned about a dozen in my lifetime. One was a AKC purebred Lab that I won at a DU banquet and one was a "pick of the litter" Springer Spaniel ( American Field Class). His name was Ascots Sir Lawrence of Ostego, Ozzie is what we called him. He was a hunting fool and the best hunting dog for ducks, pheasants and partridge that I ever hunted over. The rest were half breed hunters (both breeds need to be a hunting breed) and I feel they are not as high strung as a lot of the pure breds I've witnessed. That makes them much easier to train.
Another important thing when getting a dog is a requirement that they use when someone gets a seeing eye dog. The dog is given to the owner before the dog is 7 weeks old. Sometime after the 7 week old mark the dog does what is called "imprinting". This when the dog becomes aware of his master, the environment that he is in and considers it home. If the dog can imprint with you around him, feeding him, playing and petting him he makes a strong bond to you and will become very loyal to you. When training a dog use the same word or phrase always, for instance don't use no one time and the next time use "stop it". It confuses the dog.
I would recommend a book titled "Best way to train a dog" by Delmer Smith, a famous dog trainer from Oklahoma. Its a great read, and I found it to be a big help.
To quote a saying of his " I've known a lot of dog trainers who were said to be good, but the fact is it was the dog who made it possible"
another point; He is your dog, you feed him, take care of him and the only one he has to please is you. There will be times when your hunting with friends the dog may have a bad day. It happened to me and it was one of these friend of a friend deals. We were pheasant hunting in Iowa and was hunting standing corn, the dog got in the corn, there was a pile of birds in there and he could see them. He broke and started chasing them and was at the end of the field and birds were flying everywhere and no one was getting any shooting. When he got to the end of the field he came back to me, I scolded him and then he hunted like he was supposed to. When we got through the field everyone and myself wasn't to pleased with his performance. Walked some grassey fence lines and ditches with willows and he raised quite a few birds for us. When we went to the next field this friend of a friend suggested that I leave my dog in the truck, while we walk the field. I simply asked him then why he didn't bring his dog along to hunt with. And if my dog isn't welcome then I guess I'm not welcome either, so I'll just take my dog and go somewhere else. I was a bit ticked off at him, but that brought a flood of apologys and the dog hunted well after that and we had a good day. My friend never asked him along again.