Character

The life of your personal world. They directly measure your story's worth. The only real thing it will drag you to a cross to be nailed by readers should you dirty it.

Each character has to be meaningful and impactful to a degree. They cannot be placed randomly.

The first step to making a good character is by creating or modifying their backstory.

Their story defines who they are now, and who they'll be in the future. The way they act, react, talk, walk, look, feel, and everything. It's also what invokes empathy from the readers towards them. It adds an immeasurable depth to a fanfic. It is what makes someone unique

An example would be batman. Without his backstory, he is just a paranoid and menacing vigilante with a lot of money.

With his backstory, he becomes a traumatized kid, so broken he cannot tell right from wrong anymore, forced to abide by a code in order to cage the monster he had become. A monster born in a dark grim city with no hope in sight, where all odds are against him and with so many shades of gray one cannot distinguish black from white. Where each battle is also a mental struggle. An empty life of sacrifice with no room for joy, only vengeance and the will to carry it out no matter the cost.

The second step is their name and appearance, and the meaning behind them.

Do not create a character with a name, last name, or appearance that doesn't hint at their backstory or even future story. A simple google depth about "what name means X" can invoke a dam of feelings from your readers. This is not limited to characters, since places and objects can also have names and so invoke the same reaction.

Another thing to add is the way they talk. Formal, informal, personality, regional accent, physical features… all this can bleed into the voice of a character. Make sure each character has a unique way of speaking.

The third step is their code, their limits, and the lines they do not cross.

This can only be changed when you want a character to make a radical change, like a hero becoming a villain.

The fourth step is how to make them engage in the fanfic. (wordmothers)

Major characters, such as established protagonists and antagonists, are a prerequisite in any fanfiction. But the best fanfiction writers create memorable characters that aren't canon.

The specifics will vary from one fandom to another, but regardless, you'll need to figure out who will drive the plot. These characters will be in every scene of your story or on every panel of every page. Every scene you write should show readers why they should love said characters.

As you write about the characters, try to make them topics of interest first and objects of ridicule second. What factors make these fictional entities memorable and beloved? Make sure your characters push the boundaries a bit. Aside from that, they should also have distinctive senses of humor and interesting perspectives on the world. At the same time, they should face the same existential struggles that real people do.

Next up is: Sometimes forgotten characters make the best stories. (DeviantArt)

It's easy to find thousands of fics about America or Italy, but what about TRNC or Cameroon? With fewer used characters you will have less competition, and most likely less canon info on them so you can at your own stuff without getting flames.

Now, in a fanfic where most characters already have their personalities and backstories defined by the cannon, the only thing you need is to go to the wiki or fandom of said cannon and actually read their personalities. Something that so few people do that I believe every author is either lazy or forgot their existence entirely. Study the characters, their actions and dialogues, and how they interact canonically.

(quora) Don't protect MC just because they are the MC of the fic. Let me explain, one of the users above had an example where MC gets attacked by a robber with a knife and they used their strength to escape the man with a scratch. Please don't do that. Let them get some sort of scratch, a stab, or something. It can be even good since as they improve; you stop doing this and show progress.

(quora) Don't make the main character an anti-social, unattractive nobody who gets asked 12 times to prom, has to divide his/her time between 60+ people, and everybody in their area loves. If you want to create an unpopular character, go ahead. Just give them a solid reason for being unpopular (they store bacon in their toenails).

Don't make your protagonist spend all their time dreaming, talking, or staring at their OTL (One True Love). If a character is spending that much time on one person, maybe your story should involve some therapy sessions.

Don't be afraid to go dark. Sometimes, reading about a character slipping into the darkness is far more interesting than reading about a character who goes through no development whatsoever.

Don't make someone's minority feature their main feature.

(writingtipsoasis) A sign of good fan fiction is when the characters sound just like the original characters created by the author. Also, beware of having them take actions that are out of their character – and if you do, make sure that there is a valid reason why they are acting that way.

Now, the final note. What to avoid when making them. (tvtropes and writingtipsoasis)

[Mary Sue]: If you decide to use an OC in your fanfic, please try and flesh him/her out as much as possible. If you plan to write a Self-Insert Fic, that's fine, just don't overpower your insert character. And even if you have a favorite character, don't ruin him by making him the center of everything. The mistake they often make is creating a wish–fulfillment character that is nothing more than self-insertion.

Yes, we would all love to go to Hogwarts and be friends with Harry, Ron, and Hermione, and while fan fiction seems like the perfect place to indulge in that fantasy, it will not please the readers if your character ends up being perfect. Mary Sues are always pretty, and extremely powerful, and end up saving the world.

But here is the thing – Mary Sues are frowned upon everywhere, both in the world of original fiction and in the world of fan fiction. If you do wish to create a character of your own and insert it into an existing fictional universe, then make the individual as real as possible. The character will need flaws, and might not interact with the main characters as much as you wish, but if you have a good story, the readers will love it.

[Out of Character aka OOC]: Make sure you keep true to the personalities of the cast. Even if something about the starring character is being changed, it should be changed accordingly. Anti Heroes don't become sweet and nice just because they're your waifu in high heels… cough. This also includes going overboard with mannerisms. Establish right from the start you are going to drastically change some characters if you are going that route.

[As You Know]: Remember, you are familiar with the main character, and those who start reading the fanfic are probably familiar as well. But are you going to reference specific stories from canon? Are you going to use other, less-known characters? Don't just assume the reader will know about them. Explain, even if in a nutshell, what was the event about, or which is the deal about the character.