Character creation is a difficult and complex process. I've spoken to several writers and not two of us seem to do it the same way. Some start with the "job" or "goals" of the piece and devise a character to achieve those goals. Some start with a personality type skeleton and flesh out as the piece develops.
I don't think any way is right or wrong. Whatever works for you and your writing is what you should do.
One thing I particularly like is playing with the speech patterns of characters. I've been told that if you have crafted your characters properly, then you shouldn't need dialog tags. I'm not sure that's true, but I do like it when characters are, indeed, that distinct.
In Full Circle (to be released in a couple of weeks), I created a character with a very distinct dialect. I see you rolling your eyes now. I'm not talking about the kind of writing that only Mark Twain can pull off. I'm talking about the use of idioms and speech rooted in a different time era than the other characters.
In Full Circle all of the characters are children of whatever era they were born in or created in. Some have been able to acclimate themselves to the cultural changes of the centuries and some of them have not. Kendrick is a character who is comfortable and "in place" inside the room, but uncomfortable and "out of place" in time. Byron is a very modern character and I can easily see him walking down the street of today or yesteryear. Phineas, however, is special. His life's circumstances have prevented him from fully comprehending that he isn't where he use to be. Phineas is stuck in the Old West.
This made his dialog very difficult. It became so problematic that by the end of the novel, I told my editor, Tami Parrington, that I was killing him off as soon as I could. She told me it wasn't fair to kill off characters because they are hard.
She might be right, but I'm still gunning for bumping him off.
I like reading characters like this, but they are a major pain to write. Luckily, I live in the Information Age and I have access to the internet. Finding a print resource for speech patterns, idioms and etc of the Old West proved taxing and I found this little gem…
Most of the characters in the story (and the reader too) won't know what Phineas is talking about when he refers to "Company Q" or what he really means when he says, "You done woke up the wrong passenger." Fortunately, Kendrick and Bob are there to translate what he says. I think his presence adds color and depth to the story and I recommend giving it a try. Just don't blame me if you want to kill off the character who is providing that color and depth.