Putting the "story" in "tragic backstory" lmao
Let's see, ehm ehm
- Just a spoonful of carbon copy paper and a pen, and then, choose an existing character, that you want to copy...
- Just a spoonful of color that makes no sense, and in the end, here's your delightful Mary sue!
(^ Written with "Just a spoonful of sugar" in mind ^)
Remember: your oc doesn't live in universe, universe lives for them, and ABSOLUTELY MUST BEND ITS OWN RULES to fulfil oc's wishes
step 1: come up with a character trait
step 2: congrats! you're done! just make sure it's a part of every line they ever say even if it's completely unrelated to whatever the fuck is going on
Great and memorable works never just have an OC. They always think out of the box, drown each and every line with symbolism and hope and dreams and make it all a commentary on some society. So, if you truly want to make a great "OC" these days, the best way to go would be to make them a pig and have them say "oink" at every point in the story. Oh, and make sure that you use no words other than "oink" because good works never say things straight, they always imply their message through their prose. Name your book "oink" too and you have a best-seller.
- Never, EVER give your character any interest or hobby, unless it's like, a romance so that your OC's love interest can give them a present related to it. E.g., your character is a huge fan of books, love interest shows up mid-plot to give your character the first edition of their favorite book as a present. Don't ever worry about showing your character actually reading ANY book throughout the story, tho: just pick the name of a famous classic novel, have your OC mention or quote it ONCE and boom, you're done!
Canon book lover, much interests, very hobbies, wow! - High fantasy characters are also allowed one interest (besides the main quest or main lover)... but only if they're female and only if their entire personality and plot is going to be built around that interest. Oh, forgot to mention: the interest has to be "fighting with a sword in a world where only men can use swords".
- Make sure to just tell us what the personality of your character is supposed to be... but never have them act on it. Don't worry, readers won't notice! Saying that your character is "kind-hearted" will be 100% enough for everyone to believe it, even if they're going to spend the rest of the book kicking grannies under buses!
- If your character is female, make sure she doesn't have ANY female friend ever: all other females MUST be treated as enemies, ESPECIALLY if they're good looking. The only acceptable female friend is the one who knows her place as a side character, can't compete with the main character in any way, shape or form (too shy/too ugly) and basically only serves as a cheerleader for your character.
The poor orphan boy had his village burnt.
All the inhabitants were killed except him who was taking a dump in a nearby river.
Seeing what was his (nowhere) home had become, a scorching feeling sparked inside his heart.
It was a literal heartburn because he had not eaten. His stomach acid crawled like a Linkin Park song.
Overwhelmed, the boy ran to a nearby corpse and ate its barbequed goodness.
During eating, a desire suddenly came to him.
He needs a sauce.
Thus his quest began.
He must conquer the USA for their sauces.
Do you meant like that?
Don't let your Mc come from the heart 
Throw genuine buildup and struggles, relatability and surprises out the door, nothing needs to be earned because they are perfect at everything. The perfect Mc should belittle others and force everyone to see things your way. They should never bring people together nor give those who never understood your pov a heartfelt reason to maybe better understand.
There's no such thing as too much tragic backstory. Make their family dead, their hometown, no, their whole COUNTRY or even PLANET, GALAXY OR DIMENSION obliterated, so they're the sole survivor. Have them go through a lot of traumatic experiences just for the heck of it. Make them cursed with whatever (maybe everything they touch turns into jello, idk), make them find their new family, then kill them off as well, because no happiness allowed to our wonderful OC. Oh, and the OC's personality? Make them a bubbly and happy person, remembering their sad past and turning stuff into jello only when it's convenient to the plot. 
why make an OC just put yourself in the story
Dante's inferno did great, you could be the next Dante's inferno!
He must be a powerful and omnipotent god, who has not flaws whatsoever. He must be as unrelatable as possible and solve all of his problems with a flick of his finger
When creating an OC, always remember that they are already perfect just as they are. Never plan any kind of development or character arc! All problems in your character's life should be other people's fault, and any character flaws they have should only be viewed as an issue or annoyance by antagonists and bullies, while all nice characters should see them as endearing quirks, even if they're flaws like "steals things from everyone" or "commits random acts of violence" or "never helps anyone with anything". Your OC is a precious, pure soul just trying to get through life while bad people cause them trouble.
Project your whole identity into said character and feel attacked when said character faces any criticism
Only create one OC and have their personality morph to every occasion. Having multiple OCs will spread yourself out too thin and will make it harder for people to remember. But with one, you can put all your time and effort into making them perfect.
I feel bad when authors (this is usually in fanfiction i believe, i don't read it anymore so maybe it changed) do self inserts because i feel like i can't "hate" character since they are inspired HEAVILY by real life person (ofc i never commented how annoying character is)
Serious moment here: I can't really hate characters inspired by the author themself or their friends, but when it's a blatant self-insert or really one-sided (making characters simply for the purpose of being your opinion on another person, kind of like what @saltycyka said) it just ruins the story I guess.
If you want a really weird case, look into the old webcomic MegaTokyo. It started out as a gag comic about the author and IRL friend stuck in Japan but later morphed into something really weird and there were love interests and the author's friend was later not too happy that his likeness was used in the story. I also don't think the comic ages well.
Never tell the readers your characters' names! The more the readers know about your characters, the less likely they are to care about them!
Remember, it's all about the mystery. Don't reveal any information about your characters, even when it is relevant unless your story is just about to end. This way the ending can be as satisfying as possible and the reader will love you for it!
Yeah i hate spoilers. Just let me read without telling me what's happening or what's gonna happen, s'il vous plait!
