Food, sleep, money, and society
Ten years ago, before I had had any novels published, as a rule of thumb I constructed a small list of things that I thought all major characters in a novel should be exposed to and allowed to have individual reactions to, to make them appear particularly vivid.
Food: How does the character behave when eating with a group? If possible, how does he or she react when supplying food for others?
Sleep: What particularizes his/her going to sleep, his/her waking up?
Money: How does he or she get his/her shelter, food, and how does she or he feel about how she or he gets it?
Society: How does he or she react to somebody who makes substantially more money than he or she does, and how is this different from the way he or she acts to an economic peer (and believe me, it is different, however admirable)? How does she or he react when she or he meets somebody who makes substantially less money than he or she does (and ditto)?
In a short story, of course, one may not have time to explore all these particular aspects of this character. But I can’t think of one great novelist…who does not particularize her or his characters through at least some of these situations, somewhere or other through their books.