How do you think and write of background information on your characters?

I'm a student trying to practice on becoming a good writer(and an artist as a side job), and i'm having a lot of fun doing it. But I try to write my character's background information, but I don't know how I should write it.

Do I write their Background information based on their personality(more like today's personality)? Or something else?How do you think and write of background information on your characters?When I need a backstory for a character I always think through the people that I have known, and I ask myself which of them is most like this character.



Then I think of something I know about the real person, and I maybe adjust it a little and give it to my creation.



It works best when the fictional character is a blend of several real people - like a curry works best with more than one spice in.