A character's roots tells a lot about that character and I find that by going back on the family tree I can develop my characters and make them more real. My problem is even though I'm researching for my book either set in the west in the 1800's or in contemporary times, I have to delve into other countries and periods at times.
I remember my Social Studies classes and learning all about the "boiling pot" that makes up America. I know the only true American is the Native America who has been on this continent the longest though I've also read they came from another continent as well, long, long ago. My heritage is a "Heinz 57". My mother's side being predominately German and my Dad's side Dutch, Irish, English. So even to find my ancestral background I have to travel abroad.
That is the fun part about coming up with characters, either seeing them in my mind or having a name pop into mind and the person coming to life as I dissect the name. What is the origin of the name, can I use that to discover more about the character's family, and where they came from? How does their past make them who they are today?
Digging into what makes them who they are is first in mind before I give them blonde, brown, or red hair. Because even that may be part of their heritage. Also eye color and the tone of their skin.
I use baby name books to discover as much as I can about a name for a main character. Once I decide on the name and the heritage, I do some digging into that. When I am content the character is well-rounded in my mind and I have a general picture of them, I'll go looking for a photograph that resembles my character and put it in the file with all the notes and information about them. This is especially good when dealing with a series when characters reappearing in books.
Sometimes I'll discover a name I like, usually on grave markers in old cemeteries. Or I'll read a non-fiction historical book and I'll jot down the names that caught my eye. Then I'll go see what I can discover about that name if anything. Some appear to be male names feminized to be a name sake for a father or grandfather.