okay so picture this:

you're in those first few chapters of writing, for some reason you decided to go all the way back to the top and starting writing from season 1 of TVD, probably because you're a masochist, and so far, you're more than likely OC that happens to be related to Elena and most likely female, is simply just filling in the shoes for Elena in her quest of romancing Stefan

that, or you're following Elena everywhere as you fall in love with Damon

in the case that you're OC's love interest is Klaus, well, the most common mistake is quite literally doing every single Klaroline scene but subbing in your OC and deleting Caroline from all that

people, ya gots to stop this madness

your OC cannot munch off a pre-existing character's storyline,
it's not only lousy but downright lazy

the most common fanfictions there are (in general by the way, not just TVD universe based) is that your OC is either replacing the pre-existing love interest with the person(people) who you made the fanfic about or is just there reacting to everything and only gets an actual chapter written by the author when it comes to the OC and the OC's love interest

^^^ that's what you're gonna think of when you wanna place in your OC with someone else's storyline
"Hm, should I put my OC in that scene where Caroline and Klaus are talking about horses?" *thats when i role in looking fine as Captain America's ass* "Nope! That seat's taken! Make something new up!"

no one wants to read a script for TVD back from season 2 with a self-insert that doesn't do anything but scream when she gets attacked and cry when someone dies

get your OC to have a plot, but avoid the no-no's

- replacing a character with your OC and giving your OC that characters plot or more commonly known as the replacing Caroline from Klaroline scenes

- having your OC's only purpose in the fic to be a love interest

- stealing plots from other fandoms shows or movies

when i say 'stealing plots' i literally mean STEALING and PLOTS

not ideas or traits or creatures from other shows or movies or books.

sure, use a banshee, maybe a shapeshifter, hell even bring in the Scarlet Witch character for whatever reason

do the storyline where your OC is a descendant of Merlin or Baba Yaga or Marie Laveau of all people and how they have an apparent crown or something in the witch community

but for gods sake, i swear if anyone reading this takes the Marie Laveau descendant idea and then makes her descendant white i will become your worst nightmare and i won't be doing it alone

back to it,

remember to cite your sources, to be honest about where you got your idea to mix together something from a different show with your fanfic, it's ok if you brought in kitsune's from teen wolf, talk about why and how you're doing it

that's the great thing about fanfiction, you're in control, but there's also a difference between well written fanfiction and the stuff where a saltzman triplet is a ninja assassin who teams up with spider-man and finds out she's actually adopted and is the child of daenerys targaryen and jon snow

i mean, i mean no hate towards anyone who wants to read or write that, i'm just looking at the bigger picture if you want to write your own stories one day

- the adopted plot, Elena already went through that in season 1, not to mention it's a cliche in the fiction world already

- the reincarnation plot, especially if they have a past with other established characters, just don't, it's basically doppelgängers only they pass on the memories

- the secret sibling plot

- the plot where your OC is related to either the Mikaelsons or the Salvatores and has a past relationship with either the Salvatores or the Mikaelsons

- the soulmate plot,

god, those, when done right, could be great, but it takes a lot of effort, but usually, they aren't and turn out blagh. they always rush into it, they fall in love at first sight, and that goes for the werewolf mate thing too, those are the worst, it's basically getting two characters together and instead of establishing them as people first, they just fuck each other by the fifth chapter instead

now, if you are interested in doing a soulmate thing, well, let me at least point you in the right direction as to where you should learn,

Scaimachy by Cat

it's a Kol Mikaelson fic, and while it does play well into a lot of my no-no's like the Gilbert twin thing, it really is done well and is aware of itself, it's the one Gilbert twin fic that should exist, just ignore and erase all the others you've read

for a werewolf mate fic, let me again point you in the direction, take notes from

Bite Me by stayonbrand

it's not a TVD universe fic, but it is a werewolf/vampire boyxboy love story that is completed and well written, i will vouch for it
and it honestly does the werewolf mate thing really well, they explain it in-depth and how it's more of a longing for the other, and just a pull once you find them, you don't even know who it is until you're basically alone with them, like the wolf is confused and it's also not instant love, but it's super hilarious and it's boyxboy fic that's completed, so here i am, advertising for a really good book to get even bigger