Yesterday I wrote about letting characters grow inside your head until they are people. The next step is finding the words to convey that character's "personhood" to a reader.
It certainly isn't enough to tell what he looks like; in fact, some excellent authors refuse to write much physical description at all. Who hasn't been taken out of a story by too much detail about eye color or dewy skin? It's wise, at least in modern writing, to toss in details as casual references rather than giving extended "here's what this guy looks like" paragraphs.
But that isn't character, at least not all of it. Looks give a sense of a person, but certainly not all of him. (We know better than to fall into the trap of making all bad guys physically unappealing and all good guys wide-shouldered and well-muscled, don't we?) The trick is to reveal character indirectly and over time. In children's books characters are often named symbolically e.g., the Big Bad Wolf, or the Wicked Witch of the West, but adults expect to make their own decisions. Of course, they need clues from you, since they can't "see" the character on their own. What he does, what others say about him or do when he comes into the room, how he stands, his expression and tone of voice, and even his topics of conversation reveal who he is.
Thomas Hardy was a master of character, and his depictions of men in a pub making evening conversation strike a perfect note of rural isolation that assumes its own superiority. Conan Doyle (and now Nicholas Meyer as well) makes every word Sherlock Holmes says reveal his unconscious, snobbish egocentrism. Daphne du Maurier's narrator in Rebecca is so patently naive and uncertain that I recognize in her a certain type of girl I often met in my high school classes, the sort I yearned to shake into realizing that they were worth more than they imagined.
How do mere words create people on a page? There must be depth with a minimum of well-chosen words, reality in every action taken and word spoken. Few things irritate me more than a character who acts in a way that the author hasn't prepared me for. Among the worst is the small town sheriff who arbitrarily refuses to help a detective or even interferes with his work, just because for his stereotypical persona that's what small town sheriffs do.
No, they don't. I don't know a lot of sheriffs, true, but my guess is that they want to help solve whatever crimes they can, and if approached professionally, they will share what they know to the extent the law allows. So when a sheriff (usually with a fat belly and a red face) sneers and dismisses the protagonist, I want to scream at the author, "Two sentences could have given me a reason for this! Maybe he got burned by the last P.I. who walked into his office. Maybe he hates the guy's tie, but give me something!"
Characters are people. They have to be, or they won't work for the reader. And if the characters don't work, why should we care what happens to them?