Let’s stick to the theme of these weeks – Shanghai, 1930s.
Let’s do some “blitzkrieg characterization” (to use Michael Stackpole‘s turn of phrase).
Pick five fields (work, romance, family, hobbies etc.), and start writing a single sentence for each field, describing some this character’s background in that field.
Once you’re done, expand each sentence, adding two others.
Then, for each field, write also some contrarian detail.