The Most Common Made Mistakes In Making An Original Character
When making an OC, people are aware of the becoming of a Mary-Sue. They make these mistakes without realizing it!
*this doesn't apply to all people
~*Background*~
While having a perfect life isn't one your OC should have, (nothing unrealistic of course). A terrible life isn't one either. What are the chances of all these terrible things happening to your character? Very few. Don't overuse the melodramatic backstory that most people use in order to be... "original"
~*Flaws*~
Same with the background. While being perfect isn't something you wish to have, being terrible isn't either. Don't judge your OC by how little it's flaws are. One or two are enough, don't make him/her terrible at everything.
~*Looks*~
(Neck and up)
Be realistic my darlings, if she/he dyed her hair rainbow, be honest. Is your character going to really do it? Is he/she the type? Be sure to ask these questions before you do so. Also, along with hair color. Refrain from using the cliche style "emo-hair". If your OC does have this...cut, describe it for Pete's sake, not every 'emo' has the same hair.
~*Looks*~
(Feet and up)
To keep the haters away, don't make your OC extremely skinny or extremely fat. Neither of those are imperfect, so don't make it seem that way. As I have seen characters where they made fun of those general body types (she starved herself; she cut everyday; etc...) It's okay to experiment, but not everyone is completely depressed due to the fact they aren't what society says is beautiful.
~*Sociability*~
Don't make your OC go overboard in any direction. Period.