Dog training is more about teaching *you* how to work with your dog.
For this reason, you need a trainer that you are happy with, that you have faith and confidence in, and that proves (as in demonstrates) their method is the right one for you and your dog.
Dog training requires consistency - Body language is as much of an instruction as words too and many newbies say one thing but their movements say another. Confusion is a big factor and a decent trainer will identify these conflicts and help resolve them.
Classic one is telling a dog to Come, while running after it - The dog might see that as chasing, hunting or playing and as long as you go after, it will lead the way. But if you turn around and walk off, it will come after you.
Similarly when a dog is bad and you tell it to Come, a lot of people then scold the dog - Why the HELL would any poor puppy EVER want to Come to you again, when that's what it gets....? For example.
Dogs can't talk Human, so on behalf of your dog - When you give them an instruction, you have to ask yourself their question - "What's in it for me?".
Reward-based training is far more effective. There are several good authors, although my favourite at the minute is still Gwen Bailey. She has several books, but also does YouTubes.
Ignore anything to do with Jan Fennell as well. BIG time!!
Her whole career is built on how she magically discovered what was in fact a decades old dog-training method that "nobody else had realised" (apart from everyone who trained dogs before and had long since abandoned it as a flawed way of thinking), gave it a French name - Amichien, meaning 'Friend-Dog' - And then set about marketing it with the backing of her childhood hero, Monty Roberts the original Horse Whisperer... It's pure coincidence that Jan's "remarkable discovery" about dogs is so similar to Monty's older, longer-established and industry-proven horse training methods, as is the pure coincidence that her DOG books devote whole chapters to how wonderful this HORSE trainer is and how she's always adored him and how great it is that he endorses her stuff...
This "remarkable discovery" came to her one day, as she realised what she'd been doing wrong all this time, which had previously meant her dog apparently jumping up and putting her kid through the patio window!!
In her own book, she boasts about how well she can control her dogs, how they respect her as Pack Leader, how they hang on her every command... yet in later pages admits she can no longer take them out by herself...
She finishes by saying that her method works for every dog and if yours doesn't do what you say, you're not doing her method right. Her method is Rank Reduction, ie putting the dog down beneath you. Had we done what she suggested, our already petrified rescue Collie would be an absolute wreck.
She is so far up her own backside, you'd think she's a colorectal surgeon!!