Cesar Millan is an entertaining TV Personality, but the vet people seem outspoken against him. Specifically, there is mounds of serious research done by actual researchers (people with PhDs) which suggests that the whole pack thing is not true. With that in mind, who knows how effective the dominance approach really is?
This is where I am kind of conflicted though. I have been looking at reading some books by a few behavioral psychologists, namely Ian Dunbar, who is a Veterinarian and has a degree in Animal Behavior from Berkley. Unlike Cesar Millan, Dr. Ian Dunbar's work is actually rooted in science. I like the stuff he says about 95%, but I think there are occasions where "having control" or "being dominant" over your dog could be beneficial to your dog.
I plan on reading up on this stuff more, but I still want to caution you by noting that Cesar Millan is controversial at best in the world of dog training.