As an author, characters are an exciting part of writing because they can take on their own personalities, and do things you didn't expect when you start a work. In one book, I started with an idea of six characters. They were the holders of six powerful magical stones.
Then I needed to make six characters that were different from each other and were exciting enough that people would want to read about them for three books.
I started by numbering the characters 1-6. Then I listed some basic things about them. I described their ability (enhanced sight, hearing, strength, magic, intellect, etc.) I then moved on to give them an occupation. I thought that would be a good place to start making them different. I had a farmer, a magician, a thief, a soldier, etc. These different jobs made the characters different from the others and gave me a good place to start. When I made Kire, I originally had him as a monk, but then when I wrote the book, having some religious character didn't really fit, so I made him more of an isolated herb-ologist.
With the characters occupations I also considered how they would interact with each other. I wanted Kaz and P, for example to not really mesh at first. So he was an honest farmer, and she was a thief. The contrast of occupations made them have more tension and helped when I wanted there to be trust issues between them. It also created some awkward and fun situations.
From there I gave the characters physical characteristics, hair, eye, build, male/female, you know, the basics, and then I gave them names. I seem to be talking about Kire a lot probably because he is the one who changed the most. Kire used to be Cire. I chose that name because he was the intellect mark stone holder in the trilogy, and I just spelled my name backwards. But when push came to shove, there was confusion on how to pronounce his name, so I changed it to make it a little more obvious.
With my page filled with notes about each of the six stone holders, I started writing the story. It's really interesting that some of these stone holders are barely mentioned in the first book, but, as you will see in Book 2, they are some minor characters you see in the background. When the story evolved, the characters changed. I found myself asking, how they would honestly react to situations, and that was the direction they went.
Whether you set out the plot first, or if you write a character outline, it doesn't really matter, but both are essential parts of good storytelling, and neglecting either one will leave you with a poorly written piece, so make sure to have a great story and great people in the story.