So what, exactly, is characterisation? Put simply, characterisation is about peopling your story and fleshing out those people. Or better still, characterisation is about driving a story thorugh the response and development of your characters. By showing the reader your character in-situ, having conversations, responding to their environment and the changes they go through, and through other character's responses to them, the reader begins to visualise and understand them.
The term characterisation was introduced in 1894 as a literary term meaning a "description of essential features." Novelists like George Eliot, Flaubert and Balzac, and William Dean Howells were all writers who wrote stories where the plot was grown out character development: where character transitions or arcs were the focal point of the story. There are a range of methods that writers use to bring their characters to life. Some of these are as simple as giving them a relevant name, describing your characters, and having them perform in situations, in effect, illuminating your characters' outer life. Other techniques are much more subtle and complex and involve revealing, through action, reflection, psychology and impression, your characters' inner life.
Although whole books can, and have been written on this topic, creating a character map is a really good way to creating more juicy, interesting characters and thereby improving your stories:
If you're a visual person, why not cut out magazine pictures and paste them onto an A3 sheet, with a few details about each of your key characters. This might include not only what they look like, the clothing they wear, how they hold themselves, and the sorts of accessories or accoutrements they might gather around themselves. The resulting map could end up being quite a good visual cue for you to work with as your story develops. If you choose famous actors and actresses, you'll have a head start on the casting call for the movie which results from your book.
If you're not a visual person, then there are other good tools, including Excel, Mind Map, or just MS Word. I particularly like Mind Map (there are many open source mapping tools out there including:
The Brain: http://www.thebrain.com/c/personalbrain/?c=32, and
Free Mind: http://freemind.sourceforge.net/wiki/index.php/Main_Page
Whichever tool you use, you'll want to begin by creating a summary box or heading for each of your key protagonists, antagonists and the more prominent minor characters. Then under each of those headings, describe them, including things like what they look like, age, sex, hair, eye colour, scent, names and nicknames, politics, personality, etc.
After that you can go deeper into the internal life of your characters and the world they inhabit, teasing out their wants, needs and desires, intelligences, flaws, beliefs, motivations, history, etc, and how tht maps to the key points in your story - the character arc.
Whether you use tools, or just define your character with pen and paper, a thorough understanding of the characters and their journey in your story is the key to good fiction.
Magdalena Ball runs The Compulsive Reader. She is the author of the novels novels Black Cow and Sleep Before Evening, the poetry books Repulsion Thrust and Quark Soup, a nonfiction book The Art of Asssessment, and in collaboration with Carolyn Howard-Johnson, a number of poetry books including the recently released Sublime Planet. Find out more about Magdalena at http://www.magdalenaball.com.