Some parts sold separately - How to build a realistic OC
OCs are a growing part of the world of fanfiction. In worlds set in the far future or far past, OCs are becoming more popular.
OC actually refers to two types of characters. The first is the Original Character. Original Characters are people dreamed up by the writer to provide new interaction with familiar characters, or occasionally to tell a tale that is not part of the canon story lines. For example, Mayim Brink may be a young Middle-Eastern witch, and the fiction may be centred around her adventures, with nary a whisper of Harry or Voldemort or even Cornelius Fudge. Or perhaps you have young Haul Bloeed, a small Welsh wizard who is sorted into Hufflepuff Harry's second year, but only becomes friends with the Trio his sixth year.
The second type of OC is the Other Character. Other Characters are people in the canon Potterverse who really don't show up very often. There is a wealth of characters within the walls of Hogwarts who have no personality, no physical description (or very little) - nothing but a name. These characters, as well as the ones outside Hogwarts (the clerk at Flourish and Blotts, the man who runs Quidditch Quality Supplies) can provide unique insight and an alternate, perhaps unblemished and unbiased POV of canon events or other canon characters. (Please note; for the purpose of this essay, all Other Characters are characters mentioned in the storyline once or twice but never speak. So whereas Orla Quirke is an Other Character, Oliver Wood is not.)
Why are Other Characters so popular? There are two main reasons. One, because with an OC, you have unlimited amount of potential to work with. Even if you take an OC from the student body (say, Daphne Greengrass from Slytherin), you still get the chance to manipulate the character with very few set boundaries - Daphne, as a Slytherin, may be pure-blooded and very ambitious, but she might also believe, as Hermione does, in freedom for House Elves. Original Characters have even more leeway. You can do whatever you want.
The second reason is self-insertion, which is the bane of moderators and picky fanfiction readers alike. Self-inserted characters are generally very easy to spot, and are often boring to read. Let's be honest - few of us would make very good literary characters. We're just that boring.
So, with such a difficult issue, how does one build a perfect OC? You don't. You make a realistic OC, one that could very well exist in our own world. One of the lovely things about the Potterverse is that we all know a Harry, or a Draco, or a Hermione or even a Snape. We look at another character and go hey! I do that too! Realism counts. Perfect OCs don't.
The first steps:
First, you do the most basic outline of your character.
Unfortunately, the Hogwarts house is where a lot of good characters meet their doom. What's important to remember, if you're writing an OC, is that no person is the sum of their house. Case in point - Hermione. She's brave, but she's also hyper-intelligent (Ravenclaw), a hard-worker (Hufflepuff), ambitious and with no shortfall of cunning (Slytherin). People are multi-dimensional; no one is ever just one thing. Even characters like Draco, who are often seen as simply evil, have visible layers. Draco is rude, but also has some degree of intelligence (tricking Harry into believing there would be a duel and then setting someone on him), and is somewhat even a mama's boy.
Conversely, if you're using a canon Other Character, remember that they need a reason to be in their house - while Blaise may be a truly kind and helpful person, he's still in Slytherin, so he has ambition and cunning to spare. Some people see this as a handicap when using an OC, but you could easily show how Blaise uses his cunning and slyness to aid others. Evil and ambition aren't mutually inclusive, and neither are brains and common sense or bravery and goodwill. You can have one without the other, and that's how it often goes in the real world.
Naming your character
The Wizarding World is rife with unusual names. We have Hermione, Albus, Minerva and Draco; Luna and Orla, Lucius and Severus. But we also have Ronald and Harry, Dean and Gregory. There's a balance in the world, and one that does not apply to either the Wizarding or the Muggle worlds. It been noted several times that the vast majority of characters with more unusual names come from older Wizarding families; Hermione is somewhat of an anomaly, and JKR herself stated that Hermione's parents named her as such to show how clever they were.
One of the pet peeves of many readers are the names that are so exotic, they appear to be the scientific names for extinct species. Some names are also overused; Serena, Selena, Aurora and names of that nature have been found in literally hundreds of fanfictions, and they all tend to have the same mysterious air, sending many readers into convulsions.
So how to pick a name for the Original Character? First, look at their background. And if it's a fiction set in the past, look at any future offspring they may have. The Patil twins, Padma and Parvati, have names that come from the Hindu culture; ergo, their parents, if they attended Hogwarts, probably have Hindu names as well. They're more likely to have names like Rakesh and Sarika than Joseph and Tabitha.
While some names in the European world are interchangeable, some are very specific to where they live. Whereas Elayne is popular in several countries, Éliane is a spelling and pronunciation very specific to France. Hinrik is Icelandic, although in English-speaking countries, we would pronounce it as Henry. Moema is a Tupi (Native American) name meaning sweet, and Ngoc is Vietnamese for precious stone or jade. Mr. and Mrs. Wigglesworth of Yorkshire, England, are not likely to name their blonde-haired, blue-eyed daughter Azar, which is Persian.
So how to name your Original Character? You can give them a normal name, and then a more interesting nickname - for example, Ginevra tends to go by Ginny. Or if you're the type of person who likes to give their character's names a meaning, you can find a good name site to figure out the appropriate name.
In example : You have a male character who is spunky, but very kind, albeit a bit prone to drifting off into daydreams. He's physically tall and wiry, and has a temper that would cow Molly Weasley when he's angered.
So, perhaps for spunkiness, you find something similar to it; he has a temper that's very hot, so you think fire or the sun. So you could use Aidian, which is not unusual, but also not impossible to pronounce.
However, most Original Characters are from Western Europe or America, so foreign names like Jin-Ho or Amaretsu are pretty much out of the question. While your student doesn't have to be stuck as Sarah or Mary or Timothy, most parents are not in the habit of naming their child Absalom or Shelagh either. Your best bet is to simply scroll through a list of names and find one that's unusual - but not unheard of. Names like Cordelia or Thurstan are unusual, not incredibly strange.
On another note, I know some people will say, "But names like Neville or Parvati are really unusual!" The truth of the matter is, they're only unusual if you don't come from a certain part of the world. Seamus seems to be an exotic name to some, but if you're from Ireland, you've probably met quite a few before. Padma might sound odd, unless you come from a Hindu-intensive area. Use your common sense and you should be fine.
Avoiding the exchange student.
Exchange students are, to many readers, one of the most annoying OCs they can think of. For starters, there's absolutely no reason for Salem or Beauxbaton to be shipping all their students to Hogwarts. The popular excuse (the student's parents are moved to England) also makes no sense. It's pretty clear that Wizarding schools are boarding schools; considering how small the actual ratio of Wizards to Muggles is, there's no way that any Wizarding school could get away with being a so-called regular school. Even if a parent moved, the child would probably remain at that school.
So, you want to add an OC but want to avoid the exchange student? Pick someone from inside the Hogwarts Wall. Aside from the main students that we all know and love (or loathe), we have plenty of others. There are two invisible Gryffindor girls in Harry's year. We have Terry Boot and Mandy Brocklehust and Lisa Turpin. You can create an Original Character and simply explain that she never registered on Harry's radar before. Why would she? He's been focused on other things.
Why Mary-Sue and Gary-Stu must die.
Mary and Gary (those impossibly perfect buffoons) are hated by all. There are two main reasons - they're obnoxious to read, and they're extremely boring.
They're obnoxious because they're extremely flat characters. It might seem odd, because one would think that a character who could do everything would be extremely exciting, but they're not. Perfect people do not exist. Everyone has flaws. People who border on perfect in the real world generally don't have loads of friends either, and tend to have no personality. Additionally, a perfect character tends to be either redundant or a paradox, and not the interesting type of paradox.
They're boring because there's no room for character development. The most annoying Mary-Sue is the girl who's basically a regurgitation of Hermione, with Quidditch skills and the ability to turn into an Animagus, and minus Hermione's bossiness. How is she going to grow? Hermione is the most Mary-Sued canon character in fanfiction, but if you take a step back, Hermione is far from perfect. But because of her imperfections, we love her, and she's grown. Remember what an uptight little fuss-budget she was when we were first introduced to her? Now we cheer whenever she breaks a rule. She was interesting to begin with, because she was so intelligent and obviously had wonderful logical skills, but she's developed. Now she'll do what it takes, even if she has to break the rules, and she can relax a little now. If your character is perfect, she can't evolve. And there's simply no fun in that.
Strengths, Flaws and Weaknesses
Again, one of the problems with a Mary-Sue is that she has no flaws and weaknesses, and this goes back to the whole idea of being boring. Everyone has flaws, and that's what makes people interesting.
What often helps is to make a little chart that explains your characters strengths and weaknesses. However, one thing that irritates readers is when the concept of a flaw/weakness is misunderstood. Being ill is not a flaw. Getting tragically scarred and having your face messed up is not a flaw. Having your parents die is not a flaw. It's not part of your personality, that's part of your past. A personality flaw would be more like Hermione's bossiness, Harry's habit of not being able to think logically when he's mad, Draco's rudeness or Ron's temper. A personality flaw is something that we could potentially fix, as people, but often won't.
Example chart (strengths and weaknesses)
Intelligent/Shrewd/Kind-hearted/Helpful--Bossy/Too much of an idealist/Will ignore people/tends to assume that teachers are always right/stubborn
Sweet/gentle/Herbology expert/Brave--Horrible at school/Timid to the point of almost total passiveness/low-self esteem
So long as there's some sort of balance, a character is generally realistic. No one is the best at everything. Hermione is very intelligent, but she's terrified of flying. Conversely, no one is totally bad at everything; Neville is bad at Potions, but has a gift with plants, and thus Herbology. This extends into schoolwork as well; generally speaking, there's usually at least one class that a character does badly in. Hermione can't do Divination; Harry falls asleep in History of Magic. And since we already have a character who's great at everything, there's no need for another.
Everyone has habits. Some people jiggle their legs when they sit. Others twirl their hair. You might bite your nails. In order to build your character, you need to give them little personality quirks. Maybe your character tends to get out of breath often. Perhaps their hands flutter when they're excited. Or they could tap their fingers on a desk when they're bored. They could whistle when they're nervous, blink when they're surprised. Do they scream, yell or shriek? Do they wear their hearts on their sleeves, or are they more secretive? It may not seem like much, but it makes your character more real.
There's not much advice one can give with looks. Everyone has good traits and bad traits. The world does not need more Cho Changs and Fleur Delacours. Your character does not need to be drop-dead gorgeous. Maybe they have a warm smile, or eyes that seem to dance when they're up to something. Maybe they have beautiful hair, or chocolate skin, or a surprisingly good singing voice. Maybe their laugh fills the room with its innate cheerfulness and happiness. Give them one or two good physical traits, but only if it's necessary.
The other main annoyance is that the OC is too superhuman; they're a natural Legilimens/Animagus/ Metamorphmagus/Seer/Champion Duelist/Quidditch Whiz/Wandless Magic User/animal communicator. All at the same time. How likely is that? It's not. And it's annoying. It's much more gratifying for the reader if the person has to struggle through life and problems, just like everyone else. Giving them superhuman abilities that cause Voldemort to want them badly is just… not in good taste.
Totally ignoring canon, even in an AU/OOC fic, is usually a bad idea. Wandless magic, as we've noticed, is something that tends to be the domain of younger children, pre-Hogwarts, and occasionally occurs when a character is extremely emotionally disturbed. Even Dumbledore has some very specific limits; he may not use incantations all the time, but he still uses his wand.
Along those lines, no one walks around with a sword, or a phoenix in their pocket. No one knows how to block the Avada Kedavra curse. A sixteen year old girl is probably not the epicentre of a Prophecy. Twelve-year-olds, as a general rule, cannot create a Corporeal Patronus. Don't steal ideas from other characters - make your character unique, and appropriate. The beauty of the series is that we can see bits of our lives through the story; how many of us have ever been in the situation where a friend was mad at us for doing the right thing? Maybe we don't have a Dark Lord on our tails, but we've all had times when something dark and scary was threatening to take away something we cared about. Making a character that no one can relate to turns the reader off. Great fiction is based on our ability to connect with a reader, to make them laugh at their jokes, revel in their triumphs and cry at their losses. Most of us are average, but with one or two special qualities that make us unique. The same goes for the canon HP characters; they're normal, only they have something a little different about them that makes them different, only yet somehow the same. Great characters - real characters - become our friends. Bad characters become a nuisance. Make your character human.