How to Roleplay a Sorcerer
Sorcerers are arcane spellcasters that have, to some degree or another, inherent magical power. The reasons for this can be varied. Sorcerers are known to be produced by magically rich areas, simply by virtue of diffusion of magic through the environment. They can be produced by having some ammount of magical blood in them from lineage that includes a magical creature. Sorcerers can also be produced as a side-effect of a parent having been a sorcerer or wizard. Essentially: exposure to magic produces sorcerers. The aptitude doesn't seem to be distilled by distance from its source. So if your hundredth relative was slapped upside the head by a particularly magical weapon and lived to reproduce, ignoring lingering side-effects, you have the possibility of becoming a sorcerer.
Sorcerers are, historically, only rarely sorcerers by choice. It's true that some cultures have eugenics programs that exist purely to produce and train inherent magical talent, and will have culturally sanctioned sorcerers. Most societies, however, don't mean to produce sorcerers, they just do.
Sorcererous tendencies tend to manifest around puberty in humanoid creatures, frequently earlier for already highly magical creatures. These powers generally begin as uncontrolled, unexpected and fairly dangerous. An average commoner has about four hit points, a ray of frost does 1d4+1. You can see how even a teenage sorcerer in a bit of an angry moment can rather painfully cripple someone. This means that sorcerers come to be feared, reviled or sequestered away. Nobody expects a sorcerer in the family, unless they're extremely stoic, or just plain not commoners.
Because magic works in an instinctive way for sorcerers, they already know how to wave their hands around and what words to say to produce magical effects. These things just happen to them, it's like figuring out you can close one eye at the same time as another. You don't forget it. Regardless of Neverwinter Nights mechanics, sorcerers also never change their spell selection. They don't have the option, as the spells are just another limb they've come into use of.
So the hypothetical "average" sorcerer would discover their powers in a fairly sequestered community, attempt to supress or elaborate upon them in secret, and entertain great dreams.
Sorcerers tend towards becoming a few things. Wizards, gaining their powers through extreme logic and merticulous practice, tend towards law. Sorcerers, on the other hand, learning that they are something greater than their community, a power unto themselves, if you will, tend to range towards free action. Most people that find they have powers their peers lack try to use them, if not to impress or defend themselves, then at least to aid others. Above all sorcerers tend not to be the careful, conservative spellcasters that wizards are. Sorcerers act, for better or for worse. They tend to live fast and die young, whether good or evil.
Lawful sorcerers, of course, happen as well. They tend to be people that have a bit of a breakdown after discovering their power, and becoming very afraid of what they can do to another person. They become conservative, then, through fear of themselves. Perhaps they were someone that just wanted to ignore their power and remain part of the community, but was forced out or away, as no other could handle what they could, and they needed to leave to defend it. Sorcerers are also, frequently, sent to wizards to be trained, the people sending them not understanding their power, and the wizard fairly ineffectually trying to channel it into more logical pursuits.
Not to say that all sorcerers are afraid of themselves. Some become rather absorbed in themselves, believing themselves somehow greater than their peers, and frequently attempting to rescue or aid people with their magical powers, becoming good-hearted but hopelessly romantic. Alternatively some could see their power as placing them above others, and decide it is their perogative to nurse it until they can strike back against their own community for percieved slights, operating off of a false sense of entitlement to justice.
Mechanics of Sorcery
Deciding how and why your character uses its power can be one of the greatest aspects of being a sorcerer. After all, the character has, in technicality, absoltuely no control over what spells choose to manifest themselves. Certainly, their power tends to be temprered by their personality and preferences, but they hardly know what's going to happen next. Not all magic is blowing things up. There are sorcerers that are naturally transmuters, who find that the natural laws governing gravity and physics don't apply to them, and they can manipulate the states of things in their own world in an entertaining variety of ways. 'generalist' sorcerers also tend to be fairly rare, as people who are completely neutral and don't care what powers they posess tend not to have the force of personality required for sorcery.
Charisma, to a sorcerer, is essentially a measurement of how overbearing their presence is to the world. How much of a dent they make in society by their existance, how much people are inclined to listen to them, and how much the weave of magic they can sink into. It is, for all intents and purposes, the "weight" of your personality. In this way, it gives sorcerers power. You can elbow a bit more compliance out of the weave with a bit more weight.
Another fun aspect of creating a sorcerer is determining the source of their power. They may not even be aware of this source, and it may not even come up, but the way in which it can influence the way your character acts can be a bit of a subtle bonus to those who figure it out.
For instance, sorcerers born on another plane tend to gravitate towards powers that would be closely associated with that plane. A sorcerer born on the Inner Plane of fire, or any genasi, really, would be more likely to harness and evocate using the element from which it is derived. Negatasi frequently become necromancers, residents of the upper planes become frequently illusionists, if chaotic, or abjurers or diviners, if lawful.
If the sorcerer's power came from a creature in their lineage, they likely will still have some traits of that creature loitering around in their bloodstream. This doesn't mean to immediately make the leap of logic to 'dragon' and make your character a dragon disciple. There are literally hundreds of creatures that humans could have cross-bred with that would produce sorcerers. This doesn't mean flip open the Monster Manual and choose arbitrarily, but certainly put some thought into the idea of what monstrous or humanoid creature could be in your bloodstream to produce a sorcerer. The creature could also influence the type of powers that choose to manifest. If one is a sorcerer derivitive of an Alcor, then have them manifest primarily frost based spells. Although Neverwinter Nights mechanics don't allow for the same plethora of spells available to a Pen and Paper sorcerer, there's still enough of a selection to show a bit of racial bias.