I hunt with two labs in the field and sproul is right, seperate them, train for Obediance first...this one is important, if your dog is obediant no matter the situation your chances of having an obediant field dog are a lot better.
Play with wings and birds too, the first part of bird-dog is BIRD. Most of all have fun with it, keep your temper in check and realize consistancy is the key. There's tons of literature on dog training out there, try a magazine to start with...Gun Dog& The Retriever Journal are great magazines and indespensible to me.
I personally take all training advice with a grain of salt. I take what I need to train the dog the way I want the dog trained and leave all the whooy.
What really helped me in the begining was reading about pack mentality, realizing what alpha behavior was and adjusting our lives to take the alpha role.IE no dogs on furniture, no door crashing, crate training, waiting at meal times for release...etc.
Good luck!