It's funny you should ask that question, because I never know what my main character's name will be until I actually put the first sentence on the page. Then as soon as I know who my character is the name comes to me. For my first novel, If I Could Be Like Jennifer Taylor I knew that my secondary character's name would be Jennifer Taylor. I just thought she looked like someone who would have that name. Any Jennifer I had ever met seemed to be living in another atmosphere. They are usually beautiful, thin and popular. However, I didn't know what my main character's name should be. I wanted her to have a name you could remember and one that was in the normal range. In other words I wanted her name to reflect her. She is a nice, fairly normal girl who happens to have a little bit of a problem that causes her to be bullied. So Carol wouldn't work, because that is not a name you would remember, but Carolyn does work. Carolyn is someone you can remember. Also it pairs very well with her last name, Carolyn Samuels.
For her friends I also wanted names that would show they were normal too. Also I wanted them to have catchy names easy to remember too. So I picked Becky and Janie. They had to have names that would not only be normal, but would set them apart from the usual names. Jennifer's friends had to have exotic names almost like movie stars. Her friend Maura is an example of that kind of name. Maura also lives up to her name. She is one of those people who has lived in a world above Carolyn's along with Jennifer. The name conjures up someone who might not be so nice.
On the other hand, Jennifer's boyfriend had to have a romantic name. So I chose Brad, because all the Brads I have ever read about have been handsome hunks. That is what Brad is. Also it is a movie star name, think Brad Pitt, but he has blonde hair. This Brad has dark hair. The other guy in the book is John, but we won't talk about him here, because you have to read the book, If I Could Be Like Jennifer Taylor to find out where he fits.
For my second novel, After, I wanted the heroine to have a more active name. She is athletic and needed a name that fitted that so I named her Lauren. She also needed to be a little girly too. So Lauren is the name that fits here too. Lauren's best friend had to have a name that would be easy going and friendly as well as memorable so I chose Joey. For the doctor who was a jerk in real life I named him Dr. Jerker. When you read about him you will realize why I named him that. For the mean girl I named her Amber, because I wanted her to have a sultry and mean name and I thought that fitted her so well. I'm not saying all Ambers are like the one in this book, but the name fits her perfectly. She is a spoiled brat who is used to having her daddy get her everything and she is not accustomed to losing anything. Lauren's girl friend needed to have an inviting and friendly name so I named her Jenny. Finally, there is male character named Darren who pops up later and he needed to have a name that would fit a good looking friendly boy. Again, I won't tell you his role. It would spoil the story.
In conclusion, I think naming characters depends on their characteristics. Also it hinges on what name comes to my mind when I think about my character. After all I am the author and these characters were created by me. What I like best is that once you do name your character they take on their own life and become much more than you imagined when you first thought of them. For you, maybe you will find another way to name your characters, but I am very happy to have shared my method with all of you.