As always with these sustained posts, I reach a point where I begin to hate that I ever started them. But then I get them done, and move on, and forget that they were ever written at all - which has become my nature. There are people who write things down so they won't forget; I have discovered that after such a long time, I write things down so that I can forget. In other words, it is a process of getting rid of thoughts, getting them out of my brain and making room for other things.
But this is where I am now, so let's move on:
This would seem the obvious thing for any D&D player. The character itself, yes? Not the character and its behavior towards others, or the character and its beliefs, but the character.
Which means what, exactly?
When in doubt, always return to the word's etymology. The word was first used to define persons in a play or novel in the 17th century, in reference to the qualities that individual had - but the word is much older, older than even Latin. "Character" first originates from the description of writing and the images that preceed the alphabet, and is an amalgam of two Greek words: kharax, that means 'pointed stick'; and ghera, verb, "to scrape" or to scratch. So in terms of roleplaying games, an astute word to describe the process by which the imagined entity comes into existence.
If we reduce that process to its barest level, then, we are speaking of the creation of symbolic representations for an abstract ideal: this imaginary being, scratched out, to give it identity.
What facts do we know? Well, we're given a representation of its abilities; we have a list of its skills and knowledge, along with its limitations. Some of these things are chosen, and some are inherent (meaning that a die has been used to conjure the vicissitudes of nature). It is up to us to deconstruct these elements to piece together the entity's defining qualities.
This may be, for some, a methodology that bears similarity to counting the angels on the head of a pin. But I put it to you, if you seek to create a living character, you must give it more than the existence it has in mid-life - the point where you wish to employ the character - and embrace the entity's whole existence, as it was born, as it grew, and as it came to a realization that it wished to pursue this vocation, or that it was compelled to accept these habits, or that it found its success depended upon those sacrifices, due to whatever conditions existed.
List off some base facts and work from there: Our character is male, he is strong and constitutional, not that dextrous, and average in intellect, wisdom and charisma; he is a fighter; his preferred weapon is a battle axe; he's massive in build, both weight and height.
Very well, why a battle axe? Yes, the player chose that, and for reasons that suit the player, but how did it come about that the character swings the battle axe? When did he learn; was he unable to use other weapons; or is his particular upper body strength suited for the double-bladed weapon? Did he find himself unsatisfied with the parrying and thrusting of the sword, or was he overmanaged by the morning star's ball swinging wilding from its chain? Perhaps he loves the cutting sweep of the blade; or perhaps a hero of his used such a weapon, a hero he speaks fondly that he remembers from his childhood. Perhaps the wood in his hands reminds him of his home, so that the very act of holding the heavy handle in his hands brings him a sense of nostalgia.
He's a massive fellow now, yes, but was he always? Was he larger than other children of his village, or did he sprout later than most? Perhaps he was clumsier as a child, huge and not grown fully into his size, causing other children to laugh at his great size so that he's never truly grown comfortable with his physique. He may be large, but there's a real chance that he continues to relate to the much smaller boy who was taunted mercilessly. Perhaps he remembers when that small boy tried to attack, only to fall over his own feet, and into the mud, to the sound of laughter ... so that though he's a boy no longer, and able to stand up to the worst of the worst, the sounds of mirth still strike at his core. Or, rather, he might have been a bully; a stomping, pushing monster of a child, who grew up with his childhood friends perpetually in fear of him - and now that he's an adult, he feels strangely disquieted that these others he travels with don't seem to fear him, whereas they should.
His intelligence is 10, so he is not a stupid man; but it has always been less than easy for him to learn new things right off. He's had to repeat things over and over to get the correct, because while he can understand when something is explained to him, his memory is poor and that understanding drains off like rain from the leaves. And perhaps he is more nearly able to understand the intellectual struggles of someone who is less bright than he is, for he has some things in common with the village dunce. There is the real possibility that this fighter resents much brighter people; it isn't so bad when he's dealing with others who might latch onto an idea faster than him, but when it comes to the uncommonly genius, who are always correct and who never question their knowledge, he retains a deep and abiding hatred. Conversely, he might be in worship of people brighter than him; so much that he happily will listen to long descriptions of things he can't quite understand, recognizing that the world of knowledge or thought is much greater than he's able to grasp for himself - but it feels good knowing that its out there.
And his charisma is 11. Is it all because he's not much of a looker? Or is he a fairly appealing chap, as long as he keeps his mouth shut? Maybe its not so much that he's abusive, or obnoxious ... he might be a very pleasant fellow, except for the nasal quality of his voice that in no way results from anything he has control over. Or he might be a witty conversationalist, with fair talents for humor, except that he looks like a wart that's been filled with botox and left in the sun a bit long. It's not his fault. Get to know him and he's good company, but years of experience have taught him to stand at the back of the party when entering a tavern or an inn, or to be the soul who will gratefully manage the horses while others step in to have a bit of palaver with the jeweler who's got information. He's not necessarily angry that he was touched this way - he might even look at others in the world and feel grateful that he's not mixed in with their affairs. More commonly he'll be scratched out to be bitter and angry, but there's more possiblities than that.
Each bit of the individual can be drawn out and expanded in just that manner. It takes some practice - but begin with how the aspect would have related to the individual at the youngest possible age. Incorporate influences from parents, tutors, peers or even strangers passing through town on a particular day. Conceive of some decision the character has made about his or her self - to feel happiness, or craving, or self-hatred, or hope. Bring the character forward through puberty and allow for both good things to have happened and bad things - and apply how these imagined events were railed against, or bargained with, or accepted - if, indeed, they have ever been accepted. Finally you will have a sense of character deeper than you've considered possible.
In many ways, this advice is more useful for the writer of creative fantasy fiction than for the RPG player - I don't imagine most players would go to this depth. But even a little application of the above will do wonders.