The don'ts of making an OC

Character backstory

Now this may be the most boring part, and you may have already started on the design. DON'T DO THIS. The design should be the LAST thing that you attempt. As fun as it is to get the drawing pad out (or pony creator or YouDoodle for the lazy assholes) making a good character backstory is way more important.
Since it's more important, those tips come first!
-Don't make a generic tragic backstory*. This is one of THE WORST things you can do. The whole "____ was abandoned by her parents and abused and ignored for her whole childhood!!!1!!2!4;&:3!" is incredibly cliche, and not only that, but instead of making your audience feel bad for your character, they'll feel driven away from your character. Think about this: readers want a way to escape real life problems. Maybe some of the readers have actually been abused. Reading about a character who's been abused just makes them sadder and drives them away from your character. Or maybe they could be offended by the character, especially if they cut and the character cuts too.
-Don't make OCs have psychological disorders UNLESS you actually have psychological disorders. This is a huge mistake because your character could be offensive to those who actually have psychological disorders. For example, if you make a character with depression and you don't have depression yourself, you could come off as insulting, especially if they cut. Some people have almost died from cutting. And do not EVER make a suicidal OC. This is the most offensive type. Being suicidal is classified as a psychological disorder, usually associated with depression, so it does kinda go in this tip. Anyways, if you do this, you are guaranteed to offend somebody in your audience. Usually, OCs who are suicidal enjoy cutting if the person making the OC doesn't have depression and isn't suicidal, and this is extremely offensive. Nobody likes cutting. It's just a coping mechanism. A bad one, yes, but it's used when people feel like they have no other way to cope. Do you think people ENJOY having to hide their scars? Do you think people ENJOY going to the hospital because they've lost so much blood? Do you think they ENJOY the shock of their friends and family when they finally discover their scars? NO. So please don't make these types of OCs. Ever.
-Don't make your OCs royalty. This is incredibly annoying and cliche. Yes, it was cool the first couple of times, but now it's just annoying. Making your OC the secret daughter of Queen _____ or the secret sister of Princess _____ is just cliche. And don't try that "rebellious princess/prince" thing because it doesn't work anymore. Yes, there are some cases where royalty works, but I can assure you that OCs are not one of them.
Follow these tips and you should be fine!
*NOTE: the tragic backstory rule doesn't usually apply for creepypastas. Just don't make them excessively depressing and you should be alright.