What does matter? Indirect descriptions. These descriptions are expressed by one character about another. Those indirect descriptions bring both interest and richness to the story.
When one character sees another, what he notices reveals as much about him as the other characters he's describing. For example, let's take a man who has been a loser all his life. No matter how much he tries, he ends up messing up. As a result, he's become bitter and envious of others, believing that everyone else has a better, and easier, life.
If he sees a brunette, he may describe her as "Little Miss Perfect Princess," and he may believe she has it made--doesn't have to work and has never had a hard day in her life. He'll see her polished nails and imagine she goes weekly to a manicurist. And she must have a maid, too, to keep her clothes so white and crisply pressed. She's got it all.
His envy makes him see those things that support his beliefs, despite other more subtle signs about her true position in life. He won't see that her life isn't so perfect, either. He won't notice that her "big fancy foreign car" is fifteen years old and has a ding in the fender that she couldn't afford to repair. Or that her clothes, while good quality, are well-worn with slightly baggy knees and nearly transparent elbows. Or that the cuticles on her right hand are ragged because she's right-handed and does her own nails and manicures.
He sees what he needs to see to confirm his belief that everyone else has all the luck and s better off than he is. Therefore, his descriptions of others are filled with envy. He only sees signs of wealth and an easy life, and ignores the rest.
That's just a small aspect of characterization, but an undeniably powerful one for it let's you relay important information about two characters, simultaneously. What could be better than that?
And as I'm always interested in expanding my horizons, be sure to leave your comments and tips about favorite techniques used to portray characters--whether you're a writer or a reader.