Most things in a novel are communicated using details. In many cases, the quality of fiction is equal to the quality of the conveyed details. Note that I said QUALITY. Not quantity. The details you choose to convey will determine how successfully the reader is able to put themselves into the story. Too few details and your readers won't have enough information to get involved. Too much and the story gets bogged down. It's a delicate balance.
This is also true of the details used to describe the characters in your novel. It is possible to go on and on for pages without imparting anything of any value, especially when discussing your characters. Think about the last time you asked someone to describe a person you'd never met. You'll get responses like, "He has brown hair," "He's five foot nine," or maybe, "He's got wide shoulders." None of that tells you anything important (and certainly doesn't help you pick him out of a crowd), so you ask what he is like. You'll likely hear the familiar refrain, "He's nice." Or maybe the opposite, "He's annoying." Again, this tells you nothing. Five minutes of your life you'll never get back.
Most people are really awful at describing someone in useful terms. Most descriptions are just too general, and generalizations are completely useless in fiction. Almost everyone could be described as nice in some situations, but annoying in others. These are not individual traits, and the art of characterization (at least in fiction) deals with the individual. So your job as an author is to make sure the reader understands how this character is different from all other people.
To accomplish this, you have to provide details that are specific enough that the reader can begin to construct that character in their own minds. If you do your job correctly, they should almost be able to see the character your describe. Every detail doesn't have to be completely unique to that character (let's face it, more than one person has blond hair, and many people shout when angry), but the combination of details should add up to construct a character who is immediately recognizable.
So how do you do this? First, choose the right details to convey character. Being scattered about it just doesn't work, and irrelevant details bog down your story. Don't describe the birthmark on a character's foot unless it has something to do with your story. Do they use the birthmark to identify the body? It is used in the plot in any way at all? No, then leave it out. A detail with no purpose becomes ridiculous. Make sure the plot is motivating you to reveal that detail.
Now that you've determined what details are important, you have to decide how to reveal them. Don't do it all at once because it will come off as a list. No one lists the specific details of anyone unless they've been asked to (which only rarely happens, by the way). Is a character's hair getting in her eyes? This might be a good time to casually mention her hair and eye color. Does she have pale skin? Or dark skin? Is there a casual way to reveal this (hint: Yes, there is)? You can always have another character notice physical details (as long as your using third person point-of-view), but again, only mention then if they're important to the story in some way.
When it comes to a character's personality, which is the most important part of characterization, the only good way to do it is to demonstrate personality. Use dialogue effectively to show how your character reacts to given situations. And if you've got any internal dialogue at all, make sure it reflects your character's personality. To do all this, you have to know your characters as well as you know yourself, so take some time to get to know them. Then you can impart the pertinent details to your reader.
There is a delicate balance when it comes to the details you'll need to create an effective and interesting character. Choose your details carefully, and remember that a detail is only as good as the reader who recognizes it and understands what it means. So be clear, be concise, and don't be afraid to hit 'delete' and start again.
All fiction is, or should be, character driven. The details of the plot should arise from the decisions the characters themselves make, and from the changes that occur within the characters as a result of those decisions. If you allow your characters to drive the story, the question of what happens next is easy enough to answer. You simply have to determine what your characters would naturally do next. You must keep your character in character.
The range of possible reactions of a single character will not be the same as the range of possible reactions for all characters everywhere. To illustrate this point, think of two people you know, two very different people. Propose a scenario, perhaps getting fired at work for no good reason. What are the possible reactions for each person? They'll likely be quite different. This must also be true of fictional characters. What your characters do and how they react to any given stimuli should be a direct result of personality. The personality of the character. Keep that in mind.
Think of your story, short or long, as a series of decision points. The decision points guide the story, and each decision made is a result of the personality of a given character. I'll use my first book, Arianna's Tale, as an example of this. At the beginning of the novel, Arianna sees a man in the ocean. This man has dark hair and a dark complexion, so he's obviously an Imperial. Arianna's people are at war with the Imperials. She should leave him be, letting the ocean swallow him. But, as a healer, she simply can't do that. She has to save him. Not doing so was never an option. If she hasn't save him...well, let's just say the novel would have been quite different.
If you've ever said the story was writing itself, or complained that the characters had taken over, then you already know what it feels like to allow the characters to drive the story. If you know your characters well enough, this simply happens. You don't have to think about what happens next because it really is obvious. This applies to dialogue as well as plot, by which I mean you don't have to agonize over every line of dialogue. The characters speak the way they speak, and they never speak out of character.
If, however, you don't really know your characters, you're in for a long haul. The story will get bogged down, the plot ends up going nowhere, and the dialogue falls flat. If this is happening to you, take a close look at your characters. Get to know them. Find out their backstories, write monologues in their voices, and maybe even interview your character.
Ack! Interviewing your own character? Yep. Sit down and ask them questions, both relating to the story and totally independent of it. How would each character answer these questions? This may take some careful thought, but it will be well worth the effort. Once the characters are truly alive for you, once their have realized their own voices, they'll have more power in your story. Your plot will benefit from it, and you'll have a better than even chance than even chance that readers will connect with your characters.
You could always go the other way and force the characters to go where you want them to go, but the story will forever have a false feel to it. Plot and character are too deeply connected to isolate from each other. If your characters aren't right, the plot will also be off.
Remember, the plot only makes sense if the character can deliver it effortlessly. So keep your characters in character.
