In any disipline there is a vast difference between the theoretical and the practical (except, perhaps, theoretical physics, lol), dog training included. The goal should be a working knowledge of all aspects of dog training, which includes, but is not limited to:
breeds: their original purpose, temperment, limitations, breed specific instinctive drive, working capabilities, knowledge of bloodlines in working dogs.
Dog training theory: what is current, outdated, and why. What works and what doesn't and why. This includes going to seminars (or reading) of every disipline, even one your not currently working in. Even one you don't agree with. How to train a dog to be a seeing eye dog, seizure alert dogs, narc dogs, SAR, agility, purely positive, tracking, herding, earth dog events, lure coursing....you get the idea. How do they teach the dogs to do what they do? Usually, for the most sucessful, it is working with the dog's inate drives.
Problem dogs: aggression all types; fear related problems all types; the untrained dog/owner.
Dog learning theory: This is the most important, IMHO. How do dog's learn? How to make them learn faster? How do you 'read' a dog?
Human learning theory ('cause if your gonna be a dog trainer, most times, your training the owner, and people are a lot harder to train than dogs)
For me, this is what I would have under my belt before I would pay one dollar for a dog training school. Most of this info is available at the local library (or they can do an inter library loan and get it for you), and in various depths, the videos. But for the theory, the books are best. For the method, the videos are best.
Finally, again before I spent any money on a cert., I would use these principles and apply it to my own dog, and then volunteer at the shelter and train a whole bunch a dogs using the same principles; helps the dogs, a well trained dog is more likely to get adopted, and helps you, lots of new pupils with various temperments, training backgrounds.
Then, you are sure you have working knowledge of dog training theory. Then if you still feel you need it after all that, <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" /> I would look into the schools mentioned above. Or even see if you could do a 2 week modular based class on an area you have problems with. That way, you don't waste time and money on the little crap like reinforcment schedules, and can work on an area you have real problems in.
And the best advertisment for a trainer is their own dog. I cannot count how many times people have asked me about problems with their dog when I out training mine- "How come she looks at you all the time? my dog never does that. But she's so friendly, how did you stop her aggression problems? Are you a dog trainer? I have a problem with my dog, he pulls on the leash so much, how do I get him to stop?' <img src="/ubbthreads/images/graemlins/wink.gif" alt="" /> And I am not a professional dog trainer!
This is the level of learning, dedication and global knowledge I would look for in a trainer, not a piece of paper. Sorry this is long!
Relation is reciprocity. How we are educated by children, by animals!-Martin Buber